 By 1916 Kettle had published more than ten books and pamphlets, contributed numerous articles to journals and newspapers on Irish politics, literary reviews, poetry and essays, philosophical treatises and translations from German and French.Although at times melancholy at the war's immense escalating intensity across Europe, consuming ever more men and causing destruction to its nations, he continued to apply to be sent to the Western Front on active service, until, with his health somewhat improved, he received a commission into the 9th Battalion of the Royal Dublin Fusiliers, amidst the 16th (Irish) Division, which in early 1916 he went to France with, serving alongside Emmet Dalton, a 19 year old subaltern, whose family Kettle had known and frequented the Dublin home of pre-war.The conditions in the trenches of the Western Front broke his health again, and he returned to Dublin shortly after the failure of the abortive Easter Revolution on sick leave, seeing the wreckage of the city's centre caused by the fighting that had occurred there.