Complex sentence: On 29 September 1916 the 1st and 2nd Regiments formed an Infantry Battalion, just over two weeks later, on 15 October 1916 it became know as 13th (Scottish Horse Yeomanry) Battalion, the Black Watch.
Split into simpler sentences: On 29 September 1916 the 1st and 2nd Regiments formed an infantry battalion. Just over two weeks later, on 15 October 1916, it became know as 13th (Scottish Horse Yeomanry) Battalion, the Black Watch.