An idea for a World War I historical novel

 From my beloved late husband, Timothy Balraj:

World War I era historical novel, including the 1918 flu pandemic, told from the point of view of a soldier from India; the Indian is friends with a Native American "Indian" also serving in the war; also features the sister of one of them…Alternates between war experiences and letters from the sister detailing what is happening at home. (Note Timothy had an aunt who served as a medical professional during the 1918 pandemic and died as a result. Note this idea was not worked on after 2014, and that Timothy passed away before our current-as-I-write pandemic.)