GERMAN PANZER III & IV

Panzer III
A medium tank (22 tons) with a crew of five, the main German tank in 1940-1942. Initially it had a 37mm gun (and two machine guns), but was planned for future use of bigger guns. It participated in small numbers in the invasion of Poland, but mass production began after the beginning of World War 2, with a 50mm gun . Since the new gun was too weak against Russian T-34 tanks, a more powerful 50mm gun was installed. Later types had an even bigger 75mm gun, same as that of the Panzer IV, with 64 rounds. Production ended in mid 1943, but production of a self-propelled gun version continued until the end of the war. There were also a command tank version and other versions. A total of 15,000 were produced.
Panzer IV
A medium tank (25 tons) with a crew of five, which was produced since 1936 and until the end of the war, and became the main German tank. It carried a short-barreled 75mm gun, later replaced by a stronger long-barreled 75mm gun (with 87 rounds), and two machine guns (one coaxial and one anti-aircraft on top, with 3000 rounds). Its excellent chassis remained unchanged despite many modifications and additions of extra armor, and was also the base for many variants, such as tank destroyers ( Jagdpanzer IV ), self-propelled guns and anti-aircraft guns, and others.
9,000 Panzer IV's were produced, and more would have been produced as Guderian recommended, if it was not for Hitler's obsession for complex and very expensive advanced weapons, the Panther, Tiger, and King Tiger heavy tanks in that case, which reduced the production of the Panzer IV even before they were fully developed and tested.