9th West Yorkshire Regiment - Pte/LCpl Thomas Smith

Hello all, Thank you for any help in advance.

I'm looking for information on my Great Grandfather a Thomas Smith.

I have 3 Birth Certificates for some of his children. On each one the Fathers occupation are as follows:

1937 - Private Thomas Smith 8879 (9th West Yorks - Foreman Labourer)
1940 - Lance Corporal Thomas Smith 8879 (9th West Yorks - Forman Labourer)
1941 - Private Thomas Smith 4546611 - (West Yorks - General Labourer)

I believe the 9th West Yorks, were a service battlion, but find it hard to pick up anything more.

Could anyone with more knowledge then myself, help point me in a right direction.

Regards

James