The
New Zealand Expeditionary Force War Museum Committee approached Butler to be an official New Zealand war artist because of his reputation as an artist and his New Zealand connections. Appointed with the honorary rank of captain in the New Zealand Expeditionary Force (NZEF) in September 1918, he joined the
New Zealand Division in France later that same month. He observed a number of military operations, some while under fire, during his time with the division, making drawings in a sketchbook carried for this purpose. These sketches later became the basis for his paintings. After the Armistice, he returned to France and Belgium to sketch the various New Zealand battlefield sites. Demobilised from the NZEF on 31 December 1918, Butler was privately commissioned by
Robert Heaton Rhodes and Major General Sir
Andrew Hamilton Russell, commander of the New Zealand Division, to do a further series of senior officer portraits and a number of large landscapes of New Zealand battlefield site along the
Western Front. It was Rhodes's intention to persuade the New Zealand government to purchase these works. This was agreed to in September 1921 and payment to Butler was approved, including the purchase of a further two large works and 26 smaller paintings recommended by the
New Zealand High Commissioner to the United Kingdom,
Sir James Allen. These works are now held at the National Archives in Wellington. ==Second marriage and death==