Complex sentence: Some historians argue that Britain's isolation was formally ended by the 1902 Anglo-Japanese Alliance, but that is disputed by T.G. Otte, who argues that the Anglo-Japanese Alliance actually reinforced Britain's aloofness from the Continent and the European alliance systems.
Split into simpler sentences: Some historians argue that Britain's isolation was formally ended by the 1902 Anglo-Japanese Alliance. This is disputed by T.G. Otte, who argues that the Anglo-Japanese Alliance actually reinforced Britain's aloofness from the Continent and the European alliance systems.