Complex sentence: In June, a seaplane carrier, bolstered the Allied air force, which expanded from one squadron to No.3 Wing RNAS and the 52nd Division, began to land at Helles for the Battle of'Gully Ravine' which was launched on 28 June.
Split into simpler sentences: In June, a seaplane carrier arrived, and the Allied air force was expanded from one squadron to a full wing designated "No.3 Wing RNAS". The 52nd (Lowland) Division also landed at Helles in preparation for the Battle of "Gully Ravine", which was launched on 28 June.