Complex sentence: The British Yeomanry units that had fought dismounted at Gallipoli were reinforced by a further three brigades and reorganised into eight brigades: four mounted and four dismounted, the 74th (Yeomanry) Division and a portion of the 75th Division.
Split into simpler sentences: The British Yeomanry units that had fought dismounted at Gallipoli were reinforced by a further three brigades and reorganised into eight brigades: four mounted and four dismounted. These were the 74th (Yeomanry) Division and a portion of the 75th Division.