In June 1927 Weems reported to the Command and General Staff School at Fort Leavenworth, Kansas as a student officer and following the graduation in June 1928, he returned to the Military Academy at West Point as an Assistant Instructor in the Department of Tactics. Weems served there until June 1929, when he was transferred to the Air Corps Tactical School at Langley Field, Virginia for duty as an instructor in Infantry Tactics. When the school moved to Maxwell Field at Montgomery, Alabama in 1931, Weems went with the school and continued as an instructor there until June 1933. During his time at the Air Corps Tactical School, he was promoted to Major on December 1, 1932 and organized the G.H. Weems Educational Fund to aid deserving students who are unable to finance their college education. He subsequently entered the Army War College in Washington, D.C. and following the graduation in July 1934, he entered the two-month course at Chemical Warfare School at Edgewood Arsenal, Maryland. Weems then served as the Executive Officer of the 22nd Infantry Regiment at Fort McClellan, Alabama and also Executive Officer of Fort McClellan until September 1935, when he was transferred to Fort Sam Houston, Texas for duty as Assistant Chief of Staff for Operations (G-3) of 2nd Infantry Division. In May 1939, Weems was ordered to the Caribbean and assumed duty as Chief of U.S. Military Mission to Haiti with the headquarters in Port-au-Prince. On July 1, 1940, he was promoted to the rank of lieutenant Colonel and to Colonel on January 15, 1941. He departed Haiti in November that year and received National Order of Honour and Merit in recognition of his merits during organization of Haitian Military Academy. Weems also cooperated with Bolivia and Brazil and was also decorated by that countries. Weems returned to the United States shortly before the Japanese Attack on Pearl Harbor and assumed command of 22nd Infantry Regiment now at Fort Benning, Georgia. Upon the United States entry into World War II, he was transferred to the staff of Army Infantry School at Fort Benning in February 1942 and assumed duty as Assistant Commandant of the School under Major general Leven C. Allen. For his new billet, Weems was promoted to the temporary rank of Brigadier general on September 10, 1942 and was instrumental in training more than 60,000 young Second Lieutenants of Infantry, as well as thousands of officers and enlisted personnel. He also went overseas, when he was sent to the special observation mission to the European Theater of Operations from November 1944 to January 1945 and to the Philippines from August to November 1945.