I had been invalided home from the Front; and, after spending some months in a rather depressing Convalescent Home, was given a month's sick leave. 
I was sent back to the Front after I recovered.  
mnli hypothesis: I was sent back to the Front after I recovered.   premise: I had been invalided home from the Front; and, after spending some months in a rather depressing Convalescent Home, was given a month's sick leave. 