Short answers, pulled from the story.
The T-18, sometimes called the MS-1, was the first conventional Soviet-designed tank. It was a close copy of the French Renault FT, with improved suspension and a larger turret. Series production of the MS-1 began in 1928.
Engineer Mikhail Koshkin led the design team at the Kharkiv Komintern Locomotive Plant (KhPZ) in Kharkiv. Assigned the project in 1937, Koshkin developed two competing prototypes and persuaded Stalin to approve the heavier design. The first production T-34s were completed in September 1940.
The Red Army had 23,106 tanks in June 1941, of which about 12,782 were in the five Western Military Districts facing Germany. The T-34 and KV-1 together accounted for only 7.2 percent of that force, roughly 1,861 vehicles.
The United States sent 4,102 M4A2 medium tanks to the Soviet Union under Lend-Lease. Of these, 2,007 were equipped with the original 75 mm gun and 2,095 with the more capable 76 mm gun. This total represented 18.6 percent of all Lend-Lease Shermans.
North Korea's June 1950 invasion was spearheaded by a brigade of roughly 120 T-34-85 tanks. These tanks outmatched ROK Army bazookas and American M24 Chaffee tanks in the early months of the war, driving UN forces back to the Pusan Perimeter before heavier UN armour ended their battlefield dominance.
Iraqi armoured forces used Soviet-designed T-54/55, T-62, and T-72 tanks that lacked thermal sights and laser rangefinders. Coalition tanks equipped with thermal sights could engage and destroy Iraqi tanks from more than three times the range at which Iraqi crews could respond. Iraqi steel penetrators were also ineffective against the Chobham armour of American and British tanks.