He enlisted in the United States Naval Reserve on 2 February 1927 and began World War II active duty on 13 July 1942.

During Operation Torch, the Allied amphibious landings in North Africa, on 8 November 1942, Kline was assigned to the British Royal Navy warship HMS Hartland as a member of a naval antisabotage party.

He then turned to loading ammunition clips for an automatic rifle and continued his conduct with complete disregard of his own safety until killed by a shell explosion.

While en route to shakedown at Bermuda on 6 November 1944, Kline rescued nine survivors from the U.S. Navy K-class blimp K-34, which had been forced down in a storm.

Upon arriving at Pearl Harbor, Territory of Hawaii, on 20 January 1945, Kline trained underwater demolition teams until departing on 14 February 1945 for Leyte in the Philippine Islands.

Kline made one Magic Carpet cruise to Pearl Harbor and returned 110 Pacific veterans to San Diego on 19 November 1945.

On 21 November 1945 Kline departed San Diego for the United States East Coast, arriving at Norfolk on 5 December 1945.