The Samochodnaja Ustanowka 100, or commonly known as SU-100, was developed in 1944 and used extensively in the last year of World War II, decimating many German tank units. After World War II it stayed in duty for many decades in armies around the world, including Egypt.
This was the answer on the outdated SU-85. The SU-100 was developed in 1944 as an improvement to the SU-85, built on the same chassis as the 34/85 tank. It was designed and built at the UZTM in Yekaterinburg. The SU-100 quickly proved itself to be among the best self-propelled anti-tank guns of World War II. This was quite capable of defeating the frontal arc of any German tank in service, for which Soviet soldiers gave it the nickname "Pizdets vsemu".
The development was conducted under supervision of L. I. Gorlitskiy, chief designer of all medium Soviet self-propelled guns. The work started in February 1944 and first prototype of SU-100, called "Object 138", was built in March. After intensive testing with different models of 100 mm gun Soviet engineers approved the D-10S gun for mass production. This gun was developed in Constructors Bureau of Artillery Factory No. 9 under guidance of F. F. Petrov. After the Second World War it was installed on T-54 and T-55 tanks and its derivatives were in service forty years after initial development. The hull of SU-100 had major improvements over the SU-85; the thickness of the front armour was increased from 45 to 75 mm, and the commander's workplace was made in a small sponson on the right side of the hull; combined with the commander's cupola this greatly improved the commander's effectiveness. For better ventilation two ventilator units were installed, instead of only one as in the SU-85. Mass production began in September 1944.
The SU-100 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. By July 1945, some 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 1950's in Czechoslovakia. It was withdrawn from Soviet service in 1957 but many vehicles were transferred to reserve stocks. Some exist to this day in the Russian Army holding facilities.
Later the SU serie have be followed by the ISU serie, heavier armored and built on the KV-1 chassis, the SU-100 have never share his gun, except on unsuccesfull designes like the T-VI-100.