Missing Northumberlands 2nd Battalion

[rhimsl]

While researching information regarding a Pte. William Dews of the 2nd Battalion Northumberland Fussiliers who is listed as "Died" on 24/03/15 I came across this:

There are 25 members of the 2nd Batt. Northumberland Fusiliers who are listed as "Died" between 01/02/15 to 31/03/15. 16 are listed as "Died" on 21/02/15;

4 on 22/02/15; 2 on 12/03/15; 1 on 15/02/15; 1 on 05/03/15 and 1 on 24/03/15.

Of those 25 only 3 have known graves. The other 22 have no known graves. What happen to them? Not one of the ones who "Died" on February 21-22 have known graves. Any thoughts?