His military career began in World War I, when he had the honour of meeting Winston Churchill, who later placed him in command of the 1st Airborne Division. He held various commands, until 1935, when he was the commanding officer of the 2nd Battalion, Grenadier Guards. He held that position until about the time of the outbreak of World War II, when he became Commandant of the Small Arms School. In 1940, he was given command of the 24th Guards Brigade, until Churchill, who had become Prime Minister of the United Kingdom, appointed him as commander of the 1st Airborne Division.
He held that position through the unit's fighting in North Africa, Sicily, and Italy. In 1944, he was given command of I Airborne Corps, which was stationed in Northwest Europe. He commanded that unit during the debacle at Operation Market Garden. Although Field Marshal Bernard Montgomery placed no blame on Browning, he received no further promotion from his current rank as Lieutenant General. He was given a command in Southeast Asia, and his last major military command was as General Secretary of the War Office.