Complex sentence: On 18 March 1915, the main attack was launched by the Allied fhe fleet, comprising with a supporting array of cruisers and destroyers, against the narrowest point of the Dardanelles, where the straits are wide.
Split into simpler sentences: On 18 March 1915, the main attack was launched. The fleet, comprising with a supporting array of cruisers and destroyers, sought to target the narrowest point of the Dardanelles, where the straits are wide.