During the First World War, one of the main problems on land was the so-called. positional impasse that required the creation of a special technique. Similar processes were observed in some naval theaters of military operations. To solve special problems in typical conditions in Italy, they created "sea tanks" - torpedo boats of the Grillo type.
Defense and attack
The Kingdom of Italy entered the war in May 1915, and the Austro-Hungarian Empire became its main enemy. The battles were fought both on land and in the Adriatic Sea. Over time, the Royal Italian Navy was able to form a powerful group of torpedo boats, which effectively locked the Austro-Hungarian fleet at its bases. However, it was far from complete victory.
The Austro-Hungarian Navy took into account the existing risks and took measures. All available defenses were deployed at the Pula and Split bases, from booms to coastal artillery. Ships or boats of Italy could not safely approach the distance of a cannon shot or a torpedo launch.
Of greatest interest to the Italian Naval Forces was the port of Pula, where the main forces of the enemy fleet were concentrated. A successful strike on this object could dramatically change the situation in the region - or even withdraw the Austro-Hungarian fleet from the war. However, an attack with existing means was not possible.
Original solution
Torpedo boats were seen as the most effective means against enemy surface forces, but they could not pass into the water area of Pula due to several lines of booms. However, this problem found its solution in 1917. Engineer Attilio Bisio from SVAN proposed to create a torpedo boat of a special design, adapted to overcome floating obstacles.
The essence of the new concept was to equip a light flat-bottomed boat with a pair of caterpillar chains, with the help of which it could climb over the booms. Such possibilities are reflected in the name of the concept - "barchino saltatore" ("jumping boat"). Later, the finished equipment was officially named Tank Marino ("sea tank"). By the name of the lead boat, the entire series is often referred to as Grillo ("Cricket").
At the turn of 1917-18. plans were formed. SVAN was supposed to carry out some tests, complete the "sea tank" project, and then build a series of four boats. In the coming months, the finished equipment was supposed to take part for the first time in a real attack on Poole's base.
Design features
Development work began with a search for optimal solutions. We tested several variants of the "caterpillar mover" and also determined the most advantageous hull contours. The most successful options have found application in the finished project.
The Grillo project involved the construction of a medium-sized solid-wood flat-bottomed boat. The length of the vessel is 16 m with a width of 3.1 m. Draft is only 700 mm. Displacement - 8 tons. The staff included four people.
In the central and aft parts of the hull were placed two electric motors of the Rognini and Balbo brand with a power of 10 hp each. One of them was connected to the propeller and accelerated the boat to 4 knots, the other was responsible for overcoming obstacles. A significant part of the internal volume of the hull was given over to accumulator batteries capable of providing a cruising range of up to 30 nautical miles.
Near the sides of the hull, on the deck and on the bottom, two narrow longitudinal guides in the form of metal profiles were provided. In the bow, they installed guide wheels, in the stern - guide and driving wheels. On these devices, it was proposed to install two narrow roller track chains. Some of the chain links were equipped with bent hooks to interact with an obstacle. The chain was driven by its own electric motor through one of the rear wheels.
The Grillo's armament consisted of two standard 450mm torpedoes in service with the Italian Navy. The torpedoes were transported on board drag-type vehicles. The boat was supposed to go on a combat course, open the locks of the devices and drop weapons into the water.
The special design of the torpedo boats provided for specific working methods. Due to the limited capacity of the batteries and the short cruising range, it was proposed to deliver them to the area of the enemy port using a tug. Then, with a maximum speed of 4 knots, the boat had to approach the booms and turn on the "caterpillars". With their help, obstacles were overcome, after which the crew could continue to sail. After launching the torpedoes, the Sverchok could return to the towing vehicle in the same way.
Flotilla of insects
The Tank Marino boats were simple in design, so their construction did not take long. In March 1918, the SVAN company handed over the KVMS a series of four boats, fully suitable for combat work. Preparations for the first operations began almost immediately.
The light "jumping" boats reminded the sailors of some insects. Therefore, they were assigned the names Grille, Cavalletta ("Grasshopper"), Locusta ("Locust") and Pulce ("Flea").
Three operations
The first combat operation with the participation of new torpedo boats took place on the night of 13-14 April 1918. The boats "Cavalletta" and "Pulche" with the help of destroyers-tugs got close to the Austro-Hungarian base Pula. The crews attempted to get over the booms and attack the ships in the harbor. However, it was not possible to find a passage and enter the water area, and the crews decided to return.
The return journey took some time, and the meeting with the escort ships took place already at dawn. The command of the operation considered that the destroyers with boats in tow would not have time to go to a safe distance - the enemy could have noticed and attacked them. A tough decision was made. For their own salvation and the observance of secrecy, the unique boats were flooded on the spot.
Exactly one month later, on the night of May 14, the Grillo boat left for Pula. His crew, led by Captain Mario Pellegrini, managed to find a suitable place and start crossing the booms. On the first line of four obstacles, the "stealthy" boat made a lot of noise and attracted the attention of the enemy. Nevertheless, the commander decided to continue the operation until the boat was noticed.
An Austro-Hungarian patrol was waiting for the Italians behind the second obstacle. He tried to ram the boat, but he managed to dodge the blow. The watchman opened fire and quickly hit his target. Captain Pellegrini ordered a response with torpedoes. In the confusion, the crew did not carry out all the necessary operations, and the torpedoes, leaving for the patrol, did not explode. The Italian boat sank and its crew was captured. After the war, the sailors returned home, where they received military awards.
The last episode of the Tank Marino's combat use took place the following night, May 15. This time the boat “Locusta” set off on its first trip. Already on the way to the barriers, he was noticed, illuminated with searchlights and fired upon. There was no longer any talk of a covert attack. The command of the operation recalled the boat, and he returned home safely.
Original failure
As part of the study of the original concept, the Italian KVMS ordered and received four torpedo boats capable of overcoming obstacles. All of them managed to take part in real operations and show not at all positive results. Three boats were lost in their first exits. The fourth was saved - because the enemy noticed him too early, when he could still leave.
The Locusta boat was kept in the combat strength of the fleet, but was no longer used for its intended purpose. Three operations in April-May 1918 showed the presence of a host of problems and the inability of the available "jumping boats" to solve combat missions. In addition, due to the use of an electric power plant and low performance, the boat turned out to be unsuitable for other operations.
Naturally, new boats of this type were not built. The command preferred traditional high-speed torpedo boats to unusual "tracked" vehicles. Soon, this technique again confirmed its high potential. "Locust" remained in the KVMS until 1920, after which it was written off as unnecessary.
It should be noted that in Austria-Hungary they did not know all the features of the operation of "sea tanks", and therefore became interested in the original concept. The sunken boat Grille was raised to the surface, studied and even tried to copy. However, the Austro-Hungarian copy of the Italian boat did not manage to go to sea until the end of the war. And soon this project was simply forgotten due to the presence of more important matters.
Thus, the project of the "sea tank" quickly showed its inconsistency, and it was abandoned. All the leading naval powers continued to use traditional torpedo boats. And the problem of obstacles at the entrance to the water area soon found its solution - it was bomber aviation.
