During the siege of Leningrad two divisions of MO patrol boats served at Ladoga and got the reputation of universal boats. These were the fastest battleships that could break the enemy's water communications, guard ships and assault forces, fire against the shore objects and ships of the enemy, land the assault troops and perform tactical reconnaissance. MO patrol boats got the name of "Ladoga cruisers". But most often the MO boats had to serve as convoy to guard the slow barge caravans towed by steamboats that carried food supplies for the besieged Leningrad.
The MO type boats that were a part of the body of troops of ships guarding the water district were one-deck wooden ships with the tonnage about 65 tons. Powerful plane engines gave the boat the speed of up to 25 knots (46 km per hour). Its weapons included 45 mm universal weapons and large caliber machine guns, depth bomb throwers and smoke screen positioning equipment. Its crew included 25 people.
"Submarine Chasers" often displayed heroism in the combat operations at Lake Ladoga in 1941-1944. Thus, MO-201 patrol boats under the command of P. S. Kolesnik and MO-202 under the command of A. L. Bondarev actively participated in the evacuation of artillery divisions 168, 142 and 198 that were surrounded at the northern bank of Ladoga in August 1941. During the battle for Rahmansaari island in September 1941 the MO-206 under the command of I. P. Voloshenko displayed great valor.
The MO boats often took part in the landing of intelligence specialists behind the enemy lines during the summer of 1942. Three boats often took part in these expeditions together – MO-201, MO-213 and MO-215 under the command of senior lieutenants P. S. Kolesnik, I. I. Voronin, N. P. Epikhin, under the general command of the division commander captain lieutenant P. A. Kuriat who later became the commander of the WDD (water district defense) of the main base. Their acts of bravery were mentioned in the leaflets of the fleet political department. MO-171 under the command of V. I. Kovalevsky was specially distinguished in the battle for the Sukho island on October 22, 1942, in one of the most important combat operations at Lake Ladoga.
The patrol service of MO boats at the "small" Osinovets – Kobona route which carried out the most intensive transportation of food and ammunition supplies was quite intense. The patrol service was often carried out by the MO-215 boat under the command of lieutenant N. P. Epikhin.
The MO boats of the Ladoga navy took part in the assault forces landing operation next to the Tuloksa river in June 1944 and other operations related to the liberation of the North-West from German forces.