Citation... For outstanding heroism and courage above and beyond the call of duty as executive officer of Marine Fighting Squadron 121, 1st Marine Aircraft Wing, at Guadalcanal. Engaging in almost daily combat with the enemy from 9 October to 19 November 1942, Capt. Foss personally shot down 23 Japanese planes and damaged others so severely that their destruction was extremely probable. In addition, during this period, he successfully led a large number of escort missions, skillfully covering reconnaissance, bombing, and photographic planes as well as surface craft.

On 15 January 1943, he added 3 more enemy planes to his already brilliant successes for a record of aerial combat achievement unsurpassed in this war. Boldly searching out an approaching enemy force on 25 January, Capt. Foss led his 8 F-4F Marine planes and 4 Army P-38's into action and, undaunted by tremendously superior numbers, intercepted and struck with such force that 4 Japanese fighters were shot down and the bombers were turned back without releasing a single bomb. His remarkable flying skill, inspiring leadership, and indomitable fighting spirit were distinctive factors in the defense of strategic American positions on Guadalcanal.