Complex sentence: It was renamed 100 (Yeomanry) Regiment Royal Artillery in 1993 and in 1999,266 (Gloucestershire Volunteer Artillery) Battery at Bristol joined the regiment and 202 Battery left the regiment.
Split into simpler sentences: It was renamed 100 (Yeomanry) Regiment Royal Artillery in 1993. Then in 1999,266 (Gloucestershire Volunteer Artillery) Battery at Bristol joined the regiment and 202 Battery left the regiment.