Hello

The only birth registration I can find in Rugby (district for Stretton on Dunsmore) around that time is this one:
Harry Rathbone Q1. 1908 Rugby Vol 6d. P. 643
There are 3 girls and one other boy registered in the District between 1907 and 1912. The other boy is Ernest - no other Harry or Henry.
You might be best posting a request for his military records on the Armed Forces Board - folks on there will be able to tell you where to look
