Lawson was born in Hull, East Riding of Yorkshire. He emigrated to Edmonton in 1914 where he worked as a clerk for the Hudson's Bay Company. He enlisted in the Canadian Expeditionary Force (CEF) upon the outbreak of the First World War. He joined the 9th Battalion, CEF, and variously worked at the 1st Canadian Motor Machine Gun Brigade and at Corps Headquarters. Although he is often incorrectly attributed a Military Cross for actions at the Battle of Passchendaele or the Battle of the Somme, he was twice mentioned in despatches and received the French Croix de guerre. Lawson joined as a private in 1914 and rose to the rank of warrant officer first class before commissioning. He held the rank of captain at the end of the war.