
The land now called Delaware was home for millennia to the Lenape (Delaware) and Nanticoke nations. European arrival in the 17th century brought demographic catastrophe: epidemic diseases like smallpox reduced the indigenous population by 90 percent. Swedish colonists settled at Fort Christina (modern Wilmington) in 1638, followed by Dutch conquest under Peter Stuyvesant in 1655. The English seized control in 1664. In 1737, William Penn's sons executed the fraudulent Walking Purchase—presenting a forged 1686 deed and hiring professional runners to seize 1.2 million acres of Lenape territory. The Lenape were forced westward, first to Ohio, then Missouri, Kansas, and eventually Oklahoma. The forgery was challenged in federal court in 2004 but the land was never returned.
Delaware separated from Pennsylvania on June 15, 1776, becoming a sovereign state. The "Delaware Blues" Regiment under Colonel John Haslet fought with distinction at the Battle of Long Island in August 1776 and was one of the last units to cross the Delaware with Washington. Haslet was killed at the Battle of Princeton on January 3, 1777. On September 3, 1777, the Battle of Cooch's Bridge was fought near Newark—the only major Revolutionary engagement on Delaware soil. Colonel William Maxwell's 800 marksmen engaged British and Hessian troops under Lord Cornwallis. Twenty Americans and three British were killed. The British occupied Wilmington for a month. The Loyalist Clow Rebellion in April 1778 was suppressed.
In December 1812, Britain declared a blockade of the Delaware and Chesapeake Bays. The Royal Navy under Admiral Sir John Borlase Warren arrived in February 1813. Commodore Sir John Poo Beresford bombarded Lewes for 22 hours on April 6-7, 1813—the first use of Congreve rockets against American targets. Colonel Samuel Boyer Davis commanded 3,838 Delaware militiamen in the state's defense. The Delaware Flotilla under Captain Caesar Rodney engaged a British frigate at Crow's Shoals. DuPont's powder mills on Brandywine Creek provided gunpowder for American forces. The private militia "Brandywine Rangers" was formed by the du Pont family to protect the mills. Approximately 300 Delaware soldiers who died during the winter 1812 campaign on the Niagara frontier are buried in a mass grave in Buffalo, New York.
Delaware was a slave state that remained in the Union—the only slave state not to secede. The state was deeply divided: industrial New Castle County leaned abolitionist while agricultural Kent and Sussex Counties supported slavery. Governor William Burton prevented secession on January 3, 1861. Nearly 12,000 Delawareans served in the Union Army, with approximately 2,100 killed, wounded, or missing; an estimated 2,000 served the Confederacy. Fort Delaware on Pea Patch Island became a prisoner-of-war camp holding over 33,000 Confederate prisoners, of whom approximately 2,500 died—half during a smallpox epidemic in 1863. Causes included diarrhea (315 deaths), pneumonia (243 deaths), typhoid and malaria (215 deaths), and scurvy (70 deaths). Delaware voted against the 13th Amendment on February 8, 1865, and did not ratify it until February 12, 1901—35 years after national ratification.
DuPont's facilities in Wilmington produced 40 percent of the explosives used by the Allied forces. The Cape Henlopen naval base, staffed by 800 personnel, conducted minesweeping operations in Delaware Bay. The Delaware Aeronautical Company in Claymont established the state's first military pilot training school. The 59th Pioneer Infantry Regiment—58 officers and 1,349 enlisted men—fought in the Meuse-Argonne Offensive of 1918. Approximately 10,000 Delawareans served in World War I, with 43 killed and 188 wounded.
Delaware formed part of the "vital triangle" of national defense (Norfolk-New York-Pittsburgh). Four coastal defense forts were active: Fort Miles, Fort Delaware, Fort DuPont, and Fort Saulsbury. Dravo Corporation's Wilmington shipyard launched 187 naval vessels. Over 30,000 Delawareans—one-tenth of the state's 1940 population—served in the armed forces. Prominent Delaware commanders included Lt. General Thomas Holcomb (Marine Corps Commandant), Lt. General Eugene Reybold (Chief of Army Engineers), and Vice Admiral William Purnell Blandy (Chief of Navy Ordnance).
During the Korean War (1950–1953), 12 Delaware soldiers were declared missing in action. In the Vietnam War (1963–1971), 122 Delaware citizens were killed. The Delaware Missing in Action Memorial in Dover honors their sacrifice. Delaware's military installations, including Dover Air Force Base, continue to play significant roles in modern conflicts.