Question: What shape was the bastion fort whose defense inspired the poem that the American national anthem was based on?

full_context: Document 1: Francis Scott Key: Francis Scott Key (August 1, 1779January 11, 1843) was an American lawyer, author, and amateur poet from Frederick, Maryland and later Georgetown, D.C., near Washington, D.C. who wrote the lyrics for a poem entitled at first "The Defence of Fort McHenry", which when set to an old English gentlemens' society tune, eventually became the United States' national anthem, "The Star-Spangled Banner".
Document 2: Fort Warren (Massachusetts): Fort Warren is a historic fort on the 28 acre Georges Island at the entrance to Boston Harbor. The fort is pentagonal star fort, made with stone and granite, and was constructed from 1833–1861, completed shortly after the beginning of the American Civil War. Fort Warren defended the harbor in Boston, Massachusetts, from 1861 through the end of World War II, and during the Civil War served as a prison for Confederate officers and government officials. The fort remained active through the Spanish–American War and World War I, and was re-activated during World War II. It was permanently decommissioned in 1947, and is now a tourist site. It was designated a National Historic Landmark in 1970 as a masterpiece of coastal engineering of the pre-Civil War period, and for its role in the Civil War. It was named for Revolutionary war hero Dr. Joseph Warren, who sent Paul Revere on his famous ride, and was later killed at the Battle of Bunker Hill. The name was transferred from the first Fort Warren in 1833, which was renamed Fort Winthrop.
Document 3: USS Francis Scott Key (SSBN-657): USS "Francis Scott Key" (SSBN-657), a "Benjamin Franklin"-class ballistic missile submarine, was the only ship of the United States Navy to be named for Francis Scott Key (1779–1843), an American lawyer, author, and amateur poet who wrote the poem "The Defense of Fort McHenry", which became the words to the United States' national anthem, "The Star-Spangled Banner".
Document 4: Frank Key Howard: Frank Key Howard (1826 - 1872) (also cited as Francis Key Howard) was the grandson of Francis Scott Key and Revolutionary War colonel John Eager Howard. Howard was the editor of the "Daily Exchange", a Baltimore newspaper sympathetic to the Southern cause. He was arrested without a warrant just after midnight on September 13, 1861 at his home by U.S. Major General Nathaniel Prentice Banks on the direct orders of General George B. McClellan enforcing the policy of President Abraham Lincoln. (In his book he writes that he was told by the arresting officer that the order had come from Secretary of State William Seward.) The basis for his arrest was for writing a critical editorial in his newspaper of Lincoln's suspension of the writ of habeas corpus, and criticizing the fact that the Lincoln administration had declared martial law in Baltimore and imprisoned without charge George William Brown, the mayor of Baltimore, sitting U.S. Congressman Henry May, all the police commissioners of Baltimore, and the entire city council. Lincoln's suspension of habeas corpus in Maryland had already been declared unconstitutional by U.S. Supreme Court Chief Justice Roger Taney (Howard's great-uncle by marriage) in Ex parte Merryman, but Lincoln had ignored the federal court ruling. Howard was initially confined to Fort McHenry, the same fort his grandfather Francis Scott Key saw withstand a British bombardment during the War of 1812, which inspired him to write The Star Spangled Banner, which would become the national anthem of the United States of America. He was then transferred first to Fort Lafayette in Lower New York Bay off the coast of Brooklyn, then Fort Warren in Boston.
Document 5: Fort Morgan (Alabama): Fort Morgan is a historic masonry Pentagonal bastion fort at the mouth of Mobile Bay, Alabama, United States. Named for Revolutionary War hero Daniel Morgan, it was built on the site of the earlier Fort Bowyer, an earthen and stockade type fortification involved in the final land battles of the War of 1812. Construction was completed in 1834 and it received its first garrison in March of the same year.
Document 6: USS Fort McHenry (LSD-43): USS "Fort McHenry" (LSD-43) is a "Whidbey Island"-class dock landing ship of the United States Navy. She was named for Fort McHenry, in Baltimore, Maryland, the 1814 defense of which inspired "The Star-Spangled Banner".
Document 7: Amelia Fowler: Amelia Fowler, an embroidery teacher and well-known flag preserver, was the master needle worker who restored the original Star Spangled Banner in 1914. By that time, the flag that inspired Francis Scott Key to write the United States national anthem was just "a frail piece of bunting." But Fowler called upon her patented preservation techniques to save it from further deterioration. She used dyed-to-match silk thread and employed ten assistants to reinforce the 1020 sqft relic. They anchored it onto Irish linen with 1.7 million of Fowler's special honeycomb patterned, six-sided stitches. It took eight weeks to finish the preservation process. Upon completion, she claimed the restored flag would "defy the test of time," and charged the government $1,243.
Document 8: Star-Spangled Banner (flag): The Star-Spangled Banner, or the Great Garrison Flag, was the garrison flag that flew over Fort McHenry in Baltimore Harbor during the naval portion of the Battle of Baltimore during the War of 1812. Seeing the flag during the battle inspired Francis Scott Key to write the poem "Defence of Fort M'Henry", which, retitled with the flag's name from the closing lines of the first stanza and set to the tune of "To Anacreon in Heaven" by John Stafford Smith, later became the national anthem of the United States.
Document 9: The Star-Spangled Banner: "The Star-Spangled Banner" is the national anthem of the United States of America. The lyrics come from "Defence of Fort M'Henry", a poem written on September 14, 1814, by the 35-year-old lawyer and amateur poet Francis Scott Key after witnessing the bombardment of Fort McHenry by British ships of the Royal Navy in Baltimore Harbor during the Battle of Baltimore in the War of 1812. Key was inspired by the large American flag, the Star-Spangled Banner, flying triumphantly above the fort during the American victory.
Document 10: Mary Young Pickersgill: Mary Pickersgill (born Mary Young; February 12, 1776 – October 4, 1857), was the maker of the Star Spangled Banner Flag hoisted over Fort McHenry during the Battle of Baltimore in the War of 1812. The daughter of another noted flag maker, Rebecca Young, Pickersgill learned her craft from her mother, and, in 1813, was commissioned by Major George Armistead to make a flag for Baltimore's Fort McHenry that was so large that the British would have no difficulty seeing it from a great distance. The flag was installed in August 1813, and, a year later, during the Battle of Baltimore, Francis Scott Key could see the flag while negotiating a prisoner exchange aboard a British vessel, and was inspired to pen the words that became the United States National Anthem.
Document 11: Baltimore National Heritage Area: Baltimore National Heritage Area is a federally designated National Heritage Area encompassing portions of Baltimore, Maryland, USA. The designated area includes the central portion of the city, waterfront, inner neighborhoods and portions of the city's park system. The district includes Fort McHenry and the Inner Harbor, as well as portions of the Charles Street, Falls Road, National Historic Seaport and Star Spangled Banner Maryland Scenic Byways. The Baltimore National Heritage Area was established on March 30, 2009 by the Omnibus Public Land Management Act of 2009 (Pub.L. 111–11 §7002). The designation recognizes the area's unique historic and cultural character, and is intended to stimulate economic development, tourism and historic preservation.
Document 12: Fort Mifflin: Fort Mifflin, originally called Fort Island Battery and also known as Mud Island Fort, was commissioned in 1771 and sits on Mud Island (or Deep Water Island) on the Delaware River below Philadelphia, Pennsylvania near Philadelphia International Airport. During the American Revolutionary War, the British Army bombarded and captured the fort as part of their conquest of Philadelphia in autumn 1777. The United States Army began to rebuild the fort in 1794 and continued to garrison and build on the site through the 19th century. It housed prisoners during the American Civil War. The army decommissioned Fort Mifflin for active duty infantry and artillery in 1962 however while the older portion of the fort was returned it to the City of Philadelphia; a portion of the fort's grounds are still actively used by the United States Army Corps of Engineers making it the longest fort in military use in the United States. Historic preservationists have restored the fort, which is now a National Historic Landmark.
Document 13: To Anacreon in Heaven: "The Anacreontic Song", also known by its incipit "To Anacreon in Heaven", was the official song of the Anacreontic Society, an 18th-century gentlemen's club of amateur musicians in London. Composed by John Stafford Smith, the tune was later used by several writers as a setting for their patriotic lyrics. These included two songs by Francis Scott Key, most famously his poem "Defence of Fort McHenry". The combination of Key's poem and Smith's composition became known as "The Star-Spangled Banner", which was adopted as the national anthem of the United States of America in 1931.
Document 14: Fort McHenry: Fort McHenry, in Baltimore, Maryland, is a historical American coastal pentagonal bastion fort best known for its role in the War of 1812, when it successfully defended Baltimore Harbor from an attack by the British navy from the Chesapeake Bay September 13–14, 1814. It was first built in 1798 and was used continuously by U.S. armed forces through World War I and by the Coast Guard in World War II. It was designated a national park in 1925, and in 1939 was redesignated a "National Monument and Historic Shrine".
Document 15: Battle Monument: The Battle Monument, located in Battle Monument Square on North Calvert Street between East Fayette and East Lexington Streets in Baltimore, Maryland, commemorates the Battle of Baltimore with the British fleet of the Royal Navy's bombardment of Fort McHenry, the Battle of North Point, southeast of the city in Baltimore County on the Patapsco Neck peninsula, and the stand-off on the eastern siege fortifications along Loudenschlager and Potter's Hills, later called Hampstead Hill, in what is now Patterson Park since 1827, east of town. It honors those who died during the month of September 1814 during the War of 1812. The monument lies in the middle of the street and is between the two Baltimore City Circuit Courthouses that are located on the opposite sides of North Calvert Street. It was sponsored by the City and the "Committee of Vigilance and Safety" led by Mayor Edward Johnson and military commanders: Brig. Gen. John Stricker, Maj. Gen. Samuel Smith and Lt. Col. George Armistead (of Ft. McHenry).
ground_truth: pentagonal