From the article:
Originally designed as an evolutionary replacement for the T-34 medium tank, the T-54 (and the later T-55) quickly evolved into the Soviet Union's first main battle tank. Entering full production in 1947, the T-54 and T-55 series became the most produced tank in history with up to 100,000 units eventually rolling off the assembly lines over the next 35 years.
The hallmarks of the design were its mechanical simplicity, good mobility, compact design, and the potent D-10T 100mm gun (the same weapon as used in the SU-100M). Unfortunately the compact design resulted in a cramped interior which interfered with the effective operation of the tank and its armament.
The T-54 and T-55 were liberally provided to Soviet allies and satellite states including the United Arab Republic and Syria. The Sinai Field Army had several hundred T-54 and T-55 tanks grouped in the 4th Armoured Division and the 6th Mechanised Division.
Despite many of them being fitted with infrared equipment and stabilisers, they generally fared poorly against the better utilised Israeli armour. Their poor gunnery and abysmal tactics allowed the well trained Israelis to turn back the Arab attacks, even at night.