WW1 Pension/Service Record query

[newbie]

I have found 14 pages of information for one of my ancestors - yeah 
I need some help please ...
on the first page William Inkpen No 9392 (S9392) In response to the question no 10. Do you now belong to the Army.... answers Yes, (I can't quite make out  the Regiment -  it may be the E.Surrey Rgt.)
to question 11 Have you ever served in the Army... he answers "No, Except in above in which I am now serving. "
He is enlisted with the East Surrey Regt. at the time of this enlistment he is 18yrs 8 months,
Did he have to re-enlist because of his age? Dated 16 Dec 1907.

For his service he spent 8 years 127 days,
His military History sheet reads :
18.12.07 to 4.3.10 Home
5.3.10  to 12.11.14  India - does anyone know what  or where  he would have been involved in at this time?
(can't make this out) to 18.1.15 Home
19.1.15 to 31.5.15 B.E.Force
1.5.15 to 22.4.16 Home.

Campaigns   European, 1915
Effects of Gas P2 M/19 15.5.15

I'd appreciate some help, thanks very much,
newbie

[OldBraggs]

He was in the 4th Battalion which was a volunteer battalion (part-time soldier) and in 1907 he enlisted in the Regular Army.

Steve

[newbie]

Thank you Steve, that clarifies that point nicely.
newbie