Short answers, pulled from the story.
The name changed officially on the 21st of May 1935, when Adolf Hitler replaced the old term Reichswehr with Wehrmacht. Before that date, the German defense force had been known simply as the Reichswehr since March 1921.
The structure consisted of three branches: the Heer (army), the Kriegsmarine (navy), and the Luftwaffe (air force). General Ludwig Beck added 48 tank battalions to the program in December 1935 to support these branches.
The total number of soldiers who served approached 18.2 million over the decade from 1935 to 1945. Between 1935 and 1939, 1.3 million men were drafted while 2.4 million volunteered for service.
The Wehrmacht officially dissolved on the 20th of August 1946 under Allied Control Council Law 34. The last unit surrendered to Norway on the 4th of September 1945 at an isolated weather station in Svalbard.
An estimated 300,000 to 500,000 people died during Wehrmacht Nazi security warfare in the Soviet Union. Cooperation with SS Einsatzgruppen included supplying death squads with weapons, ammunition, equipment, transport, and housing.