For the first time in the history of Soviet tank building, the tank used an NBC protection system. If radiation higher than normal was detected, pyrotechnic charges went off and automatically sealed the tank. Air sucked into the tank went through a filter that removed radioactive dust and poisonous substances, and positive pressure inside the tank prevented air from entering in other ways.
In the middle of 1957, the tank was accepted into service under the index T-55. It was supposed to begin production on January 1st, 1958, but the country was going through reforms: industry ministries were abolished and replaced with Councils of National Economy. In connection with this, no new items were introduced into production. Meanwhile, the factory needed electronic NBC protection controllers that could not be made internally. Calls and letters to the Ministry of Transport Machinebuilding went without answer, as its staff was too busy. Kartsev sent a letter to the Chelyabinsk Electrical Machinery Factory, insisting that the Ministry ordered that they send off a batch of controllers by December 31st, 1957. Without the ability to confirm that such an order was made, the factory decided to play it safe and supply the requested batch of controllers.
The first batches of the T-55 had no DShKM AA machinegun, since at modern speeds, it was impossible to shoot down an airplane with one. As NATO countries began adopting helicopters into service, the DShKM was installed near the loader's hatch. Later, in the early 1970s, it was replaced with the 12.7 mm NSV Utes machinegun.
The IDF executed a classic "blitzkrieg". Most of Egypt's aircraft were destroyed on the ground in the first few hours of the war, earning them air superiority. After that, tanks went into battle. The main force of the IDF was composed of modernized British Centurion tanks. The Israeli versions were called Sho't (whip) and Sho't Kal (light whip). The main feature of these tanks was the 105 mm L7A1 tank gun, fully capable of penetrating the T-55. The IDF lost 122 tanks on the Sinai peninsula, but the Egyptian losses were much greater: out of 935 tanks, 820 were destroyed or captured, including 82 T-55 tanks. After a slight modernization, they were adopted into service under the index Tiran-5. A part of the tanks were equipped with new American M68 guns and were called Tiran-5Sh from the word "sharir" (strong).