Merchant ships were armored during World War II

Federal Army

K. (u.) K. Warships on the Danube

Long before Austria became a sea power, the Danube Trail was trend-setting for its defense against the Turks and then for its inevitable expansion into the Balkans, as it was in the First World War. In fact, the ships of that time were of such a quality that most of them even survived the Second World War, even if they were in someone else's hands. This post is the Austro-Hungarian k. (U.) K. Dedicated to the Kriegsmarine on the Danube and its ships.

It was not until 2006 that the last patrol boat of the Austrian Armed Forces was decommissioned, which means that military river navigation for Austria and the Navy has come to an end. It is therefore easy to forget that warships always sailed on the Danube and that Linz, Vienna and Budapest were once war ports. Before the First World War, the Austro-Hungarian Danube Flotilla consisted of ten Danube monitors (small armored ships) from 300 to 600 t, equipped with 120 mm turret guns or howitzers and 70 mm cannons, as well as twelve armed, fast patrol boats and many others Units. These included armored steamers, mine ships, pontoon ships (equipped with at least two rows of floating bodies), tugs, barges (mastless boats) and medical ships. They protected the southern border of the monarchy. In association with the land power, they had to fulfill the following tasks:

  • Cleaning and securing of power lines;
  • Patrol and reporting service;
  • Reconnaissance of the river basin;
  • Attack and defense against enemy river forces;
  • Bombardment of enemy facilities and troops;
  • Support of own forces, landing protection;
  • Transport of troops and goods;
  • Laying locks.

These tasks were already fulfilled in the days of the wooden ships Nassern (small Hungarian wooden ship with oars and latin sails, forerunner of the Tschaiken), Tschaiken (relatively long, narrow rowing ships that were well adapted to the current of the Danube) and the canon barqus against the Turks at the beginning of the 16th century. Because the Danube was not only the fastest or shortest route to and from the theater of war, but it and its banks formed part of it.

River warfare was a very special form of naval warfare, because it was one-dimensional if you take into account the relatively small width of the river. Two opposing flotillas on course or opposite course could not avoid each other. In naval warfare, shipwreck usually means "wet death" as it does on the Danube. The alternative to this was stranding on the Turkish-occupied shores.

The control of the course of the river could not be achieved without that of the bank and vice versa. In addition to the water level conditions, at the time of the wooden ships, the difficult ascent (travel against the current, which could only be easily mastered with the steam engine) was an additional limitation.

The timeframe of this article spans several centuries, during which the history of the river war and thus the development of warships on the Danube made extensive history.

The historical importance of the Danube

At over 2,850 km, the Danube is the second longest river in Europe. It takes its name from the union of the two source rivers Brigach and Breg near Donaueschingen in the Black Forest and flows through or touches ten countries on its way from west to east into the Black Sea - Germany, Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine. In doing so, it connects the most diverse peoples, cultures and religions. Numerous testimonies to the long, often shared history can be found along the course of the river. The Danube expresses itself politically, among other things. as a border river and economically as an old trade route, but was used militarily for many centuries and left cultural traces, which are still evident today in significant settlement areas, monasteries, palaces, castles and fortifications on its banks. Important cities in Central Europe are lined up like a pearl necklace along the Danube: Regensburg and Passau (Germany), Linz, Krems and Vienna (Austria), Pressburg (Slovakia), Budapest (Hungary), Belgrade (Serbia) as well as Brãila and Galaþi (Romania).


  • The Danube played a major role as a trade route for metals, salt and amber as early as the prehistoric times.
  • 700 BC At first the Greeks opened up the lower Danube as a trade route.
  • In 6 AD the Roman Danube Flotilla supported Emperor Tiberius in his operations against the Marcomanni with its base in Noricum. The Romans used the river to transport troops and building materials to supply their bases. One of the most important of these in the upper river area was Carnuntum.
  • The ships of antiquity were galleys with a latin sail, as they also sailed the coasts of the seas. The team's central ram and handguns or throwing weapons served as armament.
  • Since the middle of the 1st century AD, the Romans paved the way on the Danube through legionary camps, forts and roads as the imperial border, which for them formed the northern border for almost half a millennium. When the Roman roads slowly fell into disrepair after the fall of West Rome (AD 476), the Danube remained the only efficient west-east connection.
  • From 791 to 796 Charlemagne's campaign led along the Danube against the Avars. The river was often crossed by means of detachable pontoon bridges, and supplies followed along the Danube.
  • In 1128 the Magyars undertook an invasion of Byzantine territory, which was answered by Emperor John II Komnenos in return with his Danube fleet.
  • In the Middle Ages, the Danube became a main axis of long-distance trade with Greece and India. Merchants from all over the known world met in the Danube region to conduct their business.
  • The Danube also remained a deployment route for warlike enterprises from east to west and opposite. The nomadic peoples moved from east to west along the river, not only because of the fast connection, but also because of the vital supply of water for soldiers and animals on the army campaign. In particular, at the time of the Turkish wars, the Danube was the route marked out, at the end of which Vienna marked the promising destination.
  • In 1456 the Turks lost 200 ships to the Hungarians off Belgrade.
  • 1482 to 1484 King Matthias Corvinus used in the fight against Emperor Friedrich III. his Danube fleet during the conquest of Hainburg, Klosterneuburg and Korneuburg.
  • The death of the Hungarian King Ludwig II in the Battle of Mohacs in 1526 (approx. 150 km south of Budapest) in the fight against the Ottomans enabled the Habsburgs to gain access to Hungary due to the succession rights to the St. Stephen's Crown, acquired in 1491 and confirmed in 1506. However, the country first had to be recaptured from the Ottomans. Because of the simultaneous war on two fronts against France, the Turkish wars were very changeable for Austria for a long time and only came to an end with the reorganization of the balance of power at the Berlin Congress in 1878.
  • Russians and Turks fought against each other on and on the lower Danube until 1916.

Wooden ships

Historical events

In 1382 Austria became a seafaring nation through the inclusion of Trieste and a sea power from 1864 to 1866 at the latest. But more important than the sea, the Danube proved to be a lifeline for the Habsburg Empire. It was the time of the wooden ships with oars (oars).

In 1440 a shipyard for building ships was built in Vienna. In the 16th century, the importance of the Danube as a war and supply route for the Danube flotilla, which had around 150 river units around 1550, was recognized against the then overpowering Turks. In 1529 the Turks besieged Vienna for the first time with the support of a Danube fleet. In 1571 the naval battle of Lepanto (today: Naupaktos, at the entrance to the Gulf of Corinth) took place, whereby only the name of the commander-in-chief of the united Christian fleets, Don Juan d’Austria, had a connection to Austria. This naval battle marked a turning point in the naval war against the Ottomans, who were prevented from further expansion in the Mediterranean area and thus displaced overland. The Balkans along the Danube towards Vienna presented themselves as a worthwhile alternative.

The second Turkish siege of Vienna took place in 1683. In 1697, Prince Eugene defeated the Turkish. While Sultan Mustafa II was crossing his cavalry and most of the artillery across the Danube by means of a ship bridge, Prince Eugen destroyed the latter with fire (a warship loaded with combustible materials or explosives that was drifting or sailing towards enemy ships and then set on fire around them as well set on fire) and destroyed artillery and foot soldiers of the Turks under the eyes of their ruler, who had to watch helplessly from the left bank. It should be noted that the Danube River was not yet regulated at that time and was much wider and the banks were marshier. Prince Eugene used the route of the Danube downstream for his advance and knew how to refuse his opponent.

In 1717, the Belgrade Fortress was conquered by sea and land forces in a joint operation. During the Austrian War of Succession (1740 to 1748), Tschaiken was used in the conquest of Passau (1741). In 1791, however, Leopold I (1790 to 1792) dissolved the Danube flotilla because of its obvious failure.

Characteristic of the wooden ships

The ships on the Danube were initially modeled on seagoing ships. In the beginning they were built larger and taller and much too cumbersome for the Danube. Although they could carry more artillery, on the other hand they were not as agile as the smaller Turkish ships. Only the construction / replica of smaller ships such as the Hungarian Nasser (also Nasseden), Tschaiken and Canonbarenquen, which the Turks also used in the middle reaches, made a successful river war possible, which contributed significantly to the displacement of the Turks from Hungary.

The now small, lower wooden ships had a shallow keel and a shallow draft and were therefore only navigable on the Danube - not in coastal waters. They had a belt drive (e.g. rudder drive) and often a simple sail rigging, which was supposed to assist on the ascent (travel upstream). Otherwise, the sailors or towing teams (towing: pulling a ship along from the bank) had to laboriously pull the boat upstream. A disadvantage of the imperial fleet was that their escape route was always upstream. Their ships differed from the Turkish galleys in that they were designed for the lower course of the Danube and were therefore larger and many sailors - mostly slaves - pulled per oar, while with the imperial troops only one free man pulled per oar.

In 1764 in Klosterneuburg under shipbuilder Erik Åhsberg a typification of a newly developed Tschaike was carried out, which could be used on the upper as well as on the lower Danube. Equipped with lateral upper deck extensions, they were larger and got a stern rudder instead of the reversing rudder (as in whaling boats), although this would have allowed greater maneuverability. The commanders of the ships and flotilla were mostly English or Dutch by origin, while the crews came from the Austrian coastal countries or from the military border.

Since the operations on the Danube often lasted a long time, there was later also cooking and sleeping facilities on board for the crew, and for the officers it was not unusual for the officers to have their own cabin on long-distance journeys. In fact, the Chaiken type of ship dominated the course of the Danube for several centuries until the appearance of the steam-powered ship at the beginning of the 19th century. The last Tschaiken operated on the lower course of the Danube until around 1856.


The Tschaiken had a small cannon each on the foredeck and aft (aft), which could be rotated all around in a fork bracket. The large Tschaiken also had several on port and starboard with a limited Dwars field of fire (everything that runs across the keel line). So on the Chaiken the cannon was already the main armament, while the ram still prevailed on the galley. The river sailors (Tschaikisten) also had flintlock and side guns as well as lances on board as weapons. The side walls of the boats themselves were low and had hinged or attachable wooden walls, which were provided with loopholes for the muskets of the crew and served as a bullet trap.

The purpose of the Chaiken was

  • the education on the river,
  • support with landing and building bridges,
  • the implementation of escort tasks,
  • the transport of troops and supplies as well
  • the prevention of opposing river traffic.

Chaiken and canon barquen

A general distinction was made between Nassern, Tschaiken and Canonbaren. The Nasser were small, similar to the Zillen vehicles with little crew and no combat value. Originally, they were fishing vessels of Hungarian origin that were used by the Turks and that defected to the Danube flotilla.

A Tschaike was a small war vehicle similar to the sloop (a sailboat similar to a cutter with a mast - mostly used as a larger dinghy). The outside was made of spruce or fir, and the inside was made of oak. They were first built around 1530 in Gmunden, were made of Kraweel planking - but there was also clinker planking - with a flat bottom and a wide control section. (Kraweel planking: laterally abutting outer planking with a smooth outer skin; clinker planking: roof tile-like overlapping of the longitudinal planks, e.g. on Viking ships.) The locomotion was carried out by four to eight pairs of oars, laterally offset to one another, with each individual oar was operated by a man. Iron fittings reinforced the ends of the ship, the crew themselves were protected by attachable panels and often by a tent canopy. As armament they carried a 3-lb cannon at the front (the caliber of a cannon was given in pounds - lb; the larger the caliber, the further the cannonball flies), i. H. for a 55 mm bullet, and at the rear end a 2 lb cannon in a fork piece that was pivotably mounted for all-round fire.

Between 1526 and 1764 hundreds of Tschaiken were built in series in Gmunden. In particular, many of the larger types were launched in 1813 from the shipyard in Klosterneuburg based on designs by Erik Åhsberg. A distinction is made depending on the number of oars or the length of the ship

  • Quarter-,
  • Half and
  • Whole Chaiks.

There were even double shaiks - all of them were different! Quarter chaiks were also called patrol entchaiks; they carried a 3 lb cannon in the bow and mostly had a latin sail.

Half-chaiks were almost twice the size of the common chaiks and had a large latin sail. Their armament consisted of four 3-lb cannons each, which were mounted in a fork in the corners of the crew area.

Ganztschaiken had double latin rigging or spritsail or Lugger rigging (further development of the latin sail).

The canon barques were created after 1787, were designed as artillery carriers and were mainly stacked in Peterwardein (district of Novi Sad in Serbia). They were much larger than the Tschaiken, had 15 or more oars on both sides and a lugger mainsail with a folding mast. As armament, they carried a 24-lb cannon that could be rotated with the mount in the foredeck and a 10-lb mortar mounted on a rotatable mount aft, as well as three to four additional 3-lb cannons on each side. Their crew was 60 to 80 men, according to their size.

The Vierteltschaike was steered by a small stern rudder (the stern is a component that delimits a ship at the front or rear), while the larger chaiks were controlled by a break (front) and directional rudder (aft).

The few Danube regattas were in a class of their own. They were built from 1765 to 1769 during Maria Theresa's reign, especially in anticipation of the last Turkish war for Austria in 1788/89. The last of their generation were simply too big, too tall, and too immobile for them to fail. S.M.S. "Maria Theresia" (see pictures) was heavily armed, had considerable rigging and carried 24 cannons. It was only moved by 15 rowers on each side, which was far too little. Her strong stern rudder under the captain's cabin was noticeable in contrast to the breaker rudders (additional steering device) on the foredeck, which allowed greater maneuverability. But the time of the wooden warship was up.

Until the appearance of steam-powered ships, the Chaiken had kept the Danube free from the enemy and successfully supported their own operations, albeit with varying fortunes in war.

The display

The original monitor was a flat, two-cannon ship in a cylindrical rotating turret designed for coastal bombardment. The ship was built in 1862 by John Ericsson for the Northern States of America during the Civil War. It was the first iron warship. It sank on the march back after a draw with the casemate ship "Merrimack" of the southern states, because it was not seaworthy because of the low freeboard. After that, "Monitor" was used to designate all coastal and river armored ships or gunboats.

They were primarily artillery carriers of approx.100 to 750 t with little armor protection and several rapid-fire cannons from 70 to 180 mm. They served for

  • the control and patrol service,
  • fire support,
  • the coverage of landing and river crossing,
  • property protection as well
  • the defense against enemy forces.

Today these tasks are performed by seaworthy speedboats, littoral combatants (warships for coastal waters) or air-effect vehicles (air-cushion vehicles) with rapid-fire and missile weapons.

Iron ships

The meantime

The canon barque had reached its climax after the Napoleonic Wars. The Turkish threat was waning. The use of the steam engine in river travel promised a future in river navigation independent of the flow of the river. This is how the first armed Danube paddle steamers came into being, which were later protected against infantry shells. In 1859 there was even a screw "gunboat No. I" on the Danube before the technical breakthrough with river monitors.


Iron ships are patrol boats and river monitors (see images) with a steel structure. They were flat and wide, with a shallow draft and a shallow keel. The ships had a low silhouette with a few superstructures for passive protection. The steel structure of the monitors carried a belt, deck and superstructure armor that offered protection against light infantry gun shells. There were also some anti-balloon cannons that were completely unprotected from enemy fire, so that when the crew were shot at, casualties were often to be mourned. The monitors were equipped with modern Skoda rapid-fire guns, with rangefinders for the main armament and with combat lights.

According to their displacement, five classes can be recognized on the monitors (see table on p. 118), whereby the "Szamos" and "Temes" classes were very similar due to their tonnage and armament.

The monitors provided fire support for the land power, carried out landings and bridges, and prevented operations by opposing river forces.

Armor protection

All river monitors had two longitudinal bulkheads and many transverse bulkheads, which should represent a further factor in the descent safety. However, the longitudinal bulkheads were mainly used as coal bunkers. In general, the armor of the belt was 44 to 50 mm and the top armor 19 to 25 mm. However, in the "Leitha" class, the steel quality and strength left a lot to be desired, but this was ultimately also a question of design. The steel thickness of 44 mm was considered sufficient for "Leitha" and "Maros" than when they were rebuilt in 1894. The parts of the belt and deck, which were originally made of forged steel, were made of SM steel (Siemens-Martin steel was harder and tougher than usual Steel, since it was free of foreign elements) were replaced. All gun turrets had 75 mm armor at the front, 50 mm at the sides and 40 mm at the rear made of SM steel. Grenades from a modern medium-caliber gun could penetrate locally at close range. Older cannons, as they appeared in the Balkans at the beginning of the war, had less penetration and could not penetrate the armor. Superstructures of the "Leitha" up to a distance of 1,000 m and from S.M.S. "Szamos" can be shot through up to a distance of 300 m. Mines were the most dangerous as they deformed the entire ship frame or caused it to sink.


The Danube monitors were designed in particular as artillery carriers, i. H. they provided a stable platform for the caliber of the guns. The "Leitha" class originally carried two 150 mm cannons, which were converted to the general main armament with two 120 mm rapid-fire guns from © koda in the double turret after the conversion in 1894 . The rate of fire was eight to ten shells per minute. With a pipe length of 3.5 m (L35) they achieved a range of 10,000 m or with a pipe length of 4.5 m (L45) 12,000 m for the latest monitors.

The older ship classes "Leitha" and "Maros", which only carried a 120 mm rapid fire gun in the front turret and were defenseless from the stern, were an exception in terms of armament. The "Temes" class had a 120 mm gun turret (L35) on the foredeck to starboard and port. These towers were made of bent, riveted armored steel and have proven themselves in combat. The three other classes also carried one to three 120 mm howitzers (L10) for steep fire in recessed, modern, rotating armored domes. The secondary armament consisted of one to two 70 mm rapid-fire guns (L42; in fact, they had a caliber of 66 mm) from © koda, some of which were uncovered or mounted in armored barbeds (form of the gun substructure) on the aft part of the ship. The rate of cadence was 12 to 15 rounds per minute with the 70 mm rapid fire guns from Skoda at a range of 6,000 m. In addition, several 8 mm machine guns were mounted under armor protection for self-defense. The monitors were optimally equipped for their size and tasks.


With the exception of the two monitor classes "Enns" and "Sava", which used oil, the older classes had a coal-fired boiler for the (Yarrow) steam boilers / steam engines, which had an output of 1,200 to 1,500 hp. These propelled two propellers, which gave the monitors a speed of 9 to 14 knots (kn). The coal reserve of 46 t was sufficient for a four-day mission. The monitors were painted grass green for camouflage and had a relatively low chimney. The screws had sufficient ground clearance and protection from the rudder stem. The rudder was long and protruded over the stern post.

Patrol boats

The combat value of the patrol boats was considerably lower because of their light armament with one to four 66 mm rapid-fire cannons from © koda and one to two 8 mm machine guns (MG). They had a displacement of 15 t in the "g" and Stöhr "class, over 60 t in the" Fogos "class (two ships) and up to 133 t in the" Wels "class (four ships). The armor protection was only sufficient against handguns.The strength of the patrol boats lay in their small size and speed.They were primarily used for reconnaissance, control, escort and light support.

All ships survived the First World War under their last commander, Vice Admiral Olaf Wulff - one of the few bearers of the Maria Theresa Knight Order. After 1918 they fell to the successor states of the k.u.k. Monarchy or to the victorious powers and served with some improvements and new weapons - primarily machine weapons against aircraft - for the most part well beyond the Second World War.

Historical events

In 1878 the two Danube monitors "Leitha" and "Maros" were in use on the Sava during the occupation of Bosnia and Herzegovina. This class was modernized in 1904, then deleted in 1918 and was to be replaced by the "Ersatzleitha", but this no longer happened.

During the First World War, on July 29, 1914, the Danube monitors "Temes", "Bodrog" and "Szamos" fired the first shots at the Belgrade Fortress. From then on, the Danube flotilla took part in every major action on the Sava and Danube. Without their support, many of the land army's operations would hardly have been successful, as they provided mine clearance, artillery support and supplies of materials along the Danube. The Danube was the army's most important, fastest and most effective supply route to the southeast.

Serbia's Danube flotilla was the k.u.k. Donauflotille not grown. Still, it was not without danger. After the war began, Serbia organized all motor boats and equipped them as weapons carriers. Steamers were armored and armed. Most dangerous, however, were the drifting mines, which were moved in the direction of the river and towards the middle of the river due to the debris pushing activity of the Danube, so that neither enemy nor friend could determine their exact locations. The Austrians were primarily endangered because they ruled the Danube with their ships. The Danube flotilla also covered the withdrawal from Serbia in December 1914 and the renewed, this time successful attack on Belgrade in autumn 1915.

The SMS. "Temes I" sank with heavy losses on October 23, 1914 off Belgrade after a mine hit. On October 8, 1915, the "Temes II" (renamed S.M.S. "Bosna" after reactivation of the "Temes I" in order to avoid the duplication of the name) was put on land after a hit in the forecastle and could later be recovered and reactivated.

After Romania declared war on Austria-Hungary at the end of October 1916, the Austrian monitors fired at Giurgiu (Romanian border town on the Danube with Bulgaria), sank two Romanian patrol boats and destroyed the Romanian ship bridge near Rajhovo for the benefit of the land army under Field Marshal von Mackensen.

Romania's Danube flotilla, consisting of four large monitors that were slightly stronger than the "Temes" class, and also those of Russia, which ruled the lower Danube with ships from the Black Sea Fleet, were serious opponents. On September 22nd, 1917, at river kilometer 170, to the Romanian city of Brãila, the "Inn" was unexpectedly sunk by a mine. It was salvaged and made ready for war in Budapest in May 1918, but was no longer used.

In 1917 the monitors cleared mines and obstacles from the lower reaches of the Danube and made it possible for Austrian troops to take possession of Romanian port facilities for the transport of essential goods.

In the spring of 1918, the monitors and reconnaissance units crossed the Black Sea, although they were completely unsuitable for this because of their low freeboard (height of the ship's side above the water level), and gave the advancing troops artillery protection. They drove up the Dnieper River to Alexandrowsk (today: Zaporizhia). On October 31, 1918, during the retreat from the Balkans, the S.M.S. "Bodrog" on a sandbank near Visnica and had to be abandoned. On the other hand, 85 percent of the train of the Danube Flotilla could be saved.

The Danube Flotilla and its entourage also included many river units such as armored steamers, mine ships, pontoon ships, tugs, barges, medical ships and numerous other ships that had been captured from the enemy and put into service.

Also worth mentioning were the pontoon units of the k.u.k. Army. A special system for overcoming bodies of water was the "Herbert-Ponton", which was patented and even proved itself in the Second World War.

"Herbert" bridge ship (1913)

The bridge ship (pontoon) of "Herbert" is a catamaran, consisting of two wooden hulls that were connected to one another by a platform made of strong wooden beams. Several vehicles could be connected in the Dwars direction (across the length of a boat) to the river to form a pontoon bridge. The weight was 45 t with a 30 t load capacity, 16 m long, 3.9 m wide and 1.8 m high.

During the Second World War, the German Wehrmacht had 22 catamarans built as "Herbert" ferries with air propeller and screw drive for a speed of 17 kn and armed as landing vehicles for operation "Sea Lion" (landing in England). Only later did the "Siebel" ferry replace this system.

At a glance

What was special about the warships, the wooden ships and the ironclad ships on the Danube was their identical design: shallow, shallow draft, with low freeboard. Turrets, armor, multiple subdivisions of the hull, etc. were state of the art for river monitors. They were so well built and had long-range rapid-fire guns from © koda that many of them were still in service during the Second World War, even if they were in foreign hands. The essential thing was that the Danube flotilla had to be recognized so that these ships were already available when the occasion came, that they were used correctly and thus fulfilled all their tasks. They weren't miraculous weapons, but the nautical leadership and the sailors, who animated the ships with their combat readiness, made them an effective weapon of attack.

The Danube was not only a quick connection as a march and transport route, but it was itself a vital theater of war in the heart of the monarchy. Hardly any other waterway in the world flows through so many countries and connects so many peoples as the Danube River. What is a connection and trade route on the one hand is also a border and a military route on the other. Accordingly, there have been war fleets since ancient times that used electricity for attack / defense, for landing, transporting and withdrawing people and goods.

The hydrological conditions of the Danube led to special ship developments, which hardly differed between friend and foe. So at the time of the wooden ship, the chaiken and cannon barques were created, in the age of the iron ship the patrol boats and the armored Danube monitors with machine drives and modern armament.

Author: DI Helmut W. Malnig, born in 1933, high school diploma and training in Vienna and abroad, active as an analyst, systems engineer and project manager in the energy sector, defense technology and in aerospace at home and abroad (Germany, Canada), since 1997 retired. Numerous publications (heat transfer) and patents (defense technology) as well as articles on technical-cultural-historical topics.