Tuhia he tomokanga mo tenei waahanga - I muri i tana taenga mai ki Parani i te Hui-tanguru 1918, i tukuna a Thompson ki te waahanga o nga kaimahi matauranga (G-2) o te tari matua o te American Expeditionary Force. Mai i te Hōngongoi ki te Mahuru 1918, ko Thompson te kaiawhina mo nga kaimahi mo te Intelligence i runga i nga kaimahi o te First United States Army. I whai wāhi ia ki te whakaekenga o Aisne-Marne
me te Pakanga o Saint-Mihiel. Mai i te Mahuru 1918 ki te Paenga-whawha 1919, i mahi a Thompson hei G-2 mo te Tuarua o te US Army, tae atu ki te mahi i muri i te pakanga o te waahanga Toul. I whakatairangahia ia ki te rangatira mo te wa poto i te Oketopa 1918.