Complex sentence: The four Sikh regiments went through a number of minor name changes over the next 45 or so years: in 1857 they became "Regiment of Sikh Infantry, Punjab Irregular Force" and in 1865 "Regiment of Sikh Infantry, Punjab Frontier Force".
Split into simpler sentences: The four Sikh regiments went through a number of minor name changes over the next 45 or so years. In 1857 they became "Regiment of Sikh Infantry, Punjab Irregular Force".