During World War I, the British government wanted to push through the Dardanelles so they could threaten Istanbul and knock the Ottoman Empire out of the war. The plan that was developed to make this happen involved both land and sea forces. It failed, and Winston Churchill has historically been blamed for that failure.
The first part of the plan to capture the Dardanelles involved warships. The warships were supposed to go in and bombard Ottoman forts that guarded the straits. This was supposed to destroy the forts and let ships pass into the Black Sea. This part failed because the forts were too strong, there were mines that the Allies had not known about, and the naval commanders were not willing to press the attack strongly.
The second part of the plan was to land troops at a place called Gallipoli (and other beaches), from which they would take control of the forts and ensure the straits stayed open. This is the part that turned into a major disaster. The troops did not land soon enough, and the Ottomans had time to bring large numbers of troops to defend Gallipoli. The Allies had not expected and were not prepared to land at a defended beach. The invasion turned into a disaster. The Allies stayed for nine months, incurring tens of thousands of casualties without any result.
This was the plan the Allies intended to use to capture the Dardanelles. It failed terribly, with tremendous loss of life.