Complex sentence: In February 1917, just before the division moved forward to take part in the first battle of Gaza, the British 22nd Mounted Brigade, a yeomanry brigade from the Territorial Force, joined the division.
Split into simpler sentences: In February 1917, just before the division moving forward to take part in the first battle of Gaza. The British 22nd Mounted Brigade, a yeomanry brigade from the Territorial Force joined the division.