Butler would fly to France, attach himself to an active Fighter Squadron and join its raids, so that he could study each new German tactic at first hand, work out an effective counter to it and then go back to his school and give further instruction in the light of the information he had gained in battle.
His stay in France would sometimes extend over a period of eight weeks.
In February 1918, he received a head wound on active service over Douai, and in December of the same year he was awarded the Air Force Cross.
During his service in Great Britain, Butler discovered the advantages of a primitive form of air mail. He dropped weighted notes from his plane when time did not allow a message being sent through normal channels. As we shall see, this habit had a warming sequel on his return to South Australia.
Captain Harry Butler remained in the R.F.C until the war ended on Armistice Day, 1918.