William H. Lehner, Jr. entered military service in Wisconsin. He served in the 36th Bomber Squadron, 482nd Bomber Group, Heavy, as a Second Lieutenant and Navigator on the B24 #42-51232 'The Jig's Up' during World War II. On December 22, 1944, their aircraft crashed into the sea close to North Stack in Wales, UK. The cause of the accident was a lack of fuel that resulted in a diversion to the Anglesey Wartime Air Base. It is reported that the B24 bomber was flying in fog, and the crew did not know that they were over the sea. The pilot ordered his crew to bail out, believing they were flying over land. Only the pilot, Lt H.Boehm, and his co-pilot, D. Burch, survived. The rest of the crew members were lost to the sea and their bodies were never recovered.

2Lt Lehner was declared Missing in Action and is memorialized at the Tablets of the Missing, Cambridge American Cemetery, Cambridge, United Kingdom.