In 1929, Groves departed for Nicaragua in charge of a company of the 1st Engineers as part of an expedition whose purpose was to conduct a survey for the Inter-Oceanic Nicaragua Canal. Following the 1931 Nicaragua earthquake, Groves took over responsibility for Managua's water supply system, for which he was awarded the Nicaraguan Presidential Medal of Merit. Groves was promoted to captain on 20 October 1934. He attended the Command and General Staff School at Fort Leavenworth, Kansas, in 1935 and 1936, after which he was posted to Kansas City, Missouri, as assistant to the commander of the Missouri River Division. In 1938 and 1939 he attended the Army War College. On 1 July 1939, he was posted to the War Department General Staff in Washington, D.C.