Allied codebreakers determined the route and time schedule of the Mitsubishi G4M bomber carrying Isoroku Yamamoto by breaking the Purple code and Lanphier was selected for the mission to shoot it down. The mission was a success with both of the "Betty" bombers being destroyed. Officially, the after-action report gave Captain Lanphier and his wingman First Lieutenant Rex T. Barber each half-credit for the kill. While the USAF did not reverse its 1991 decision giving half credit to each pilot, a retired lawyer / historian and state of Oregon politicians credit Barber with the sole kill. Lanphier's claim does not stand up to the accounts given by every other battle participant including American Lightning pilots Besby Holmes, Doug Canning and Rex Barber, and Japanese Zero pilot Kenji Yanagiya. Promoted to lieutenant colonel in February 1945, Lanphier served as director of operations of the 72nd Fighter Wing of the Second Air Force until late 1945. Leaving active duty following the war, he was promoted to colonel in the Air Force Reserves in 1950. After the war he worked as an editor of the Idaho Daily Statesman and the Boise Capital News while continuing to serve as an officer and fighter pilot in the Idaho Air National Guard. He served as president of the Air Force Association from September 1947 to September 1948. In December 1949, to promote the AFA's "airability program", an aviation awareness campaign, Lanphier made a round-the-world flight using scheduled airlines, making the 22,140 mile trip in under five days. He carried with him a letter from President Harry Truman commemorating the 46th anniversary of the first flight of the Wright brothers. Upon returning to New York, the letter, postmarked in 12 countries, was delivered to AFA President Robert S. Johnson, for presentation to the Kill Devil Hills Memorial Association at its annual 17 December anniversary of the Wright's first flight at Kitty Hawk, North Carolina. He was then appointed special assistant to the Secretary of the Air Force, and then special assistant to the chairman of the National Security Resources Board. From 1951 to 1960, he was vice president of the Convair division of General Dynamics in San Diego, California. He served as the Washington liaison and was a strong proponent of the Intercontinental Ballistic Missile and Global Surveillance System in the 1950s. Mr. Lanphier was President of Fairbanks Morse from 1960 until August 1962. In 1965 he was a senior projects manager at North American Space Division in Downey, California.
Death
Lanphier died November 26, 1987, in San Diego, California, of cancer. He was buried in Arlington National Cemetery.
Fictional portrayals
Lanphier was played by actor William Schallert in the 1960 film, The Gallant Hours.
Legacy and decorations
During World War II, Colonel Lanphier was credited with downing nine Japanese planes, damaging eight on the ground, and sinking a destroyer. His decorations include:
