Final answer:
The English attacked Fort McHenry, which defended Baltimore harbor, to force its surrender, but the attack failed despite a 25-hour bombardment. This emboldened American defenses and morale, leading to the composition of what became the U.S. national anthem.
Step-by-step explanation:
The English were compelled to attack Fort McHenry because it served as the main defense for Baltimore harbor during the War of 1812. In September 1814, the British army and navy, under the command of Ross and Admiral Alexander Cochrane respectively, bombarded the fort in an attempt to force its surrender. The plan was to relentlessly bombard the fort; however, the attack lasted for twenty-five hours to no avail. Despite Cochrane's efforts, including an attempted landing of a small force for an on-land assault, the fort's defenders withstood the attack, raising a large American flag famously known as the Star Spangled Banner after the bombardment ceased. This event inspired Francis Scott Key to write the poem 'In Defense of Fort McHenry,' which later became adapted into the U.S. national anthem.
The failure of the British attack on Fort McHenry was significant because it prevented the British from capturing Baltimore and helped maintain American morale during the war. This attack and subsequent retreat marked a turning point that suggested British forces might not be able to easily overcome American defenses, even though Britain had made gains elsewhere, as in the burning of Washington D.C.