Complex sentence: Two squadrons and one troop of Berkshire Yeomanry of the 6th Mounted Brigade had taken command of the front, sending back information about the attack by infantry, mounted troops, and some machine gun crews.
Split into simpler sentences: Two squadrons and one troop of Berkshire Yeomanry (6th Mounted Brigade) defended the front. They reported being attacked by infantry, mounted troops, and some machine gun crews.