Simplify the following text for a Grade 7 native English-speaking person.
Original: He was then transferred to the British Indian Army , joining initially the Bengal Staff Corps as a Lieutenant during 1887 and being attached to the 39th Bengal Infantry , later transferring to the 29th Punjabis .
Simplified: He then joined the British Indian Army . First joining the Bengal Staff Corps as a Lieutenant in 1887 and being part of the 39th Bengal Infantry , and then joining the 29th Punjabis .