piece of observational equipment. On the other hand, the SU-100's optics were a little inferior (4x optics vs German 5x optics). For better ventilation two ventilator units were installed, instead of only one as in the SU-85. Mass production began in September 1944. Service history The SU-100 was introduced in October 1944 and quickly became popular with Soviet tank crews as its gun could penetrate virtually any German tank then in service until being outmatched by the Tiger II. The gun was excellent, being able to penetrate the Tiger I at 2 km with APCBC rounds while its APHE rounds could penetrate a max of 218 mm of armour. The SU-100 especially saw extensive service during the last year of the war. It was used en masse in Hungary in March 1945, when Soviet forces defeated the German Operation Frühlingserwachen offensive at Lake Balaton. And although not intended for it, the SU-100 was also used in the Battle of Berlin because its gun could deal with heavy fortifications. However, its lack of a machine gun made it need aircraft and infantry support. By July 1945, 2,335 SU-100s had been built. The vehicle remained in service with the Red Army well after the war; production continued in the Soviet Union until 1947 and into the 1950s in Czechoslovakia. It was withdrawn from Soviet service in 1967 but many vehicles were transferred to reserve stocks. Some exist to this day in the Russian Army holding facilities. Many Warsaw Pact countries also used the SU-100, as did Soviet allies such as Egypt, Angola and Cuba. A few SU-100 were delivered to Yugoslavia after the war, under the designation M-44. The SU-100 saw service in the fighting that accompanied the 1956 Suez Crisis, in which the Egyptians used SU-100s against Israel's M4 Sherman tanks. The vehicle was also utilized in the 1967 Six-Day War and the 1973 Yom Kippur War. It was modified slightly to adapt it to the sandy conditions of the Middle East, thus creating the SU-100M variant . Exported SU-100s continued in service until the 1970s, and in some countries, even later. Yugoslavs used them during the civil war; however, due to lack of spare parts they were quickly retired, despite their satisfactory performance. The SU-100 remains in use by the Vietnam People's Army and the Korean People's Army Ground Force. SU-100s entered service with the People's Liberation Army (PLA) of