[1] Following the outbreak of World War I in August 1914, during German invasion of Belgium, Tilkens served in the Belgian forces and was decorated for valour at the Battle of the Yser.
[1] In 1916, with emergence of static trench warfare on the Western Front, he volunteered for service in Belgian Congo where fighting had broken out on the colony's border with German East Africa.
[1] After the end of World War I in 1918, Tilkens remained in the army and rose through the ranks further, taking overall command of Belgium's artillery and, later, its Air Force.
Tilkens' tenure as Governor-General coincided with the start of the Great Depression which hit the Congo in the early 1930s and caused an economic crisis.
With the Congo's budget cut by the Belgian government, Tilkens decided to reform the entire colonial administration to create a more cheaper, more centralized system.