The Oberkommando des Heeres or OKH for short was Germany's Army's High Command from 1936 - 1945.
There also were an OKM = Oberkommando der Marine and an OKL = Oberkommando der Luftwaffe for the navy and the air force respectively.
The Army commanders (Oberbefehlshaber des Heeres, or OBdH for short) of the Wehrmacht were:
1935 to 1938 - W. von Fritsch 1938 to 19 Dec 1941 - Generalfeldmarschall Walther von Brauchitsch 19 Dec 1941 to 30 Apr 1945 - Adolf Hitler 30 Apr 1945 to 8 May 1945 - Generalfeldmarschall Ferdinand Schörner
Following German tradition the OBdH was not planning operations. This task was left to the general staff, so actually the most important man in the Army (and the Navy, but less so in the Luftwaffe, which was commanded by Hermann Goering) was the chief of the general staff (Chef des Generalstabs des Heeres, or Chef GenStdH for short). It should be noted that (since Germany always has been a land bound nation) the Heer (army) always has been the leading factor in planning campaigns. Thus there was no such thing as a combined planning of the forces. The Oberkommando der Wehrmacht (OKW), which was by definition superior to the OKH, was neither planned to nor had the resources for doing that.
Later in the war the OKH was responsible for less and less tasks. For example, the invasion of Norway was entirely planned past the OKH.
During World War II this were:
1 Sep 1939 to 24 Sep 1942 - Generaloberst Franz Halder 24 Sep 1942 to 10 June 1944 - Generaloberst Kurt Zeitzler 10 June 1944 to 21 July 1944 - Generalleutnant Adolf Heusinger 21 July 1944 to 28 Mar 1945 - Generaloberst Heinz Guderian 1 Apr 1945 to 30 Apr 1945 - General der Infanterie Hans Krebs
When Hitler took command of the army on 19 Dec 1941, the importance of the GenStdH decreased, and Hitler was responsible more and more for the operational planning.