Though its roots date back to the Continental Army of the Revolutionary War, the U.S. military did not officially get its start until September 29, 1789, when Congress passed a bill legalizing the small contingent already in uniform. Get the facts on what’s become the world’s most powerful fighting force.

Soldiers from the U.S. Army's 3rd Brigade Combat Team, 1st Infantry Division, salute during the playing of the Star Spangled Banner during a homecoming ceremony in 2014.
Soldiers from the U.S. Army’s 3rd Brigade Combat Team, 1st Infantry Division, salute during the playing of the Star Spangled Banner during a homecoming ceremony in 2014. (Credit: Luke Sharrett/Getty Images)

At the beginning, the military was practically nonexistent.

Believing that “standing armies in time of peace are inconsistent with the principles of republican governments [and] dangerous to the liberties of a free people,” the U.S. legislature disbanded the Continental Army following the Revolutionary War, except for a few dozen troops guarding munitions at West Point, New York, and Fort Pitt, Pennsylvania. Yet it also called upon four well-manned state militias to provide 700 men in order to deal with potential threats from Native Americans and the British. A reorganized version of this so-called First American Regiment essentially would be all President George Washington had at his command upon taking office in April 1789.

Washington had to remind Congress to create the military.

The ratification of the Constitution in 1788 greatly expanded the federal government’s authority, in part by giving Congress the power to raise and support armies. The First Congress did not immediately act upon this provision, however, choosing instead to set up the State, War and Treasury departments and the judiciary, among other things. On August 7, 1789, President Washington urged it to establish “some uniform and effective system” for the military “on which the honor, safety and well being of our country so evidently and essentially depend.” He made a second plea for action three days later. But it was not until September 29, the last day of its first session, that Congress passed a bill empowering the president “to call into service, from time to time, such part of the militia of the states, respectively, as he may judge necessary.” Before that, states could refuse to send along their men.

The Civil War was the bloodiest in U.S. history.

Throughout the first several decades of its existence, the United States suffered relatively few combat casualties. That all changed during the Civil War, when the Union and Confederacy lost at least 618,000 men between them—and possibly many more—to bullets and disease. In fact, it’s believed that more Americans were killed or wounded in one day of fighting at Antietam than in the entire War of 1812, itself the seventh-deadliest conflict in U.S. history. Since the Civil War, only World War II has come close in terms of American deaths, with 405,000.

The use of camouflage dates back over a century.

In 1779, George Washington chose blue as the primary uniform color of the Continental Army, a decision that remained in place as late as the Spanish-American War of 1898, when some U.S. troops in Cuba purportedly smeared mud on themselves so as to better avoid enemy snipers. Soon after, the Army adopted a khaki summer uniform and a greenish-brown winter service uniform, keeping the traditional blue only for formal occasions. More changes came during World War I, when, following the example of the French, the U.S. military formed a team of artists and other creative types to design low-visibility apparel. Allied camoufleurs, influenced by Cubism and other modern styles, also painted ships with bold, wild-looking stripes to confuse German submarines and built false bridges, decoy tanks and even paper-mache horse carcasses. Later on, neuroscientists helped to produce increasingly complex camouflage patterns, including one known as “U.S. woodland,” used primarily of late by Navy SEALs. And in 2001, the Marines introduced pixelated, computer-generated camouflage.

The first women enlisted around World War I.

During the Revolutionary War, American women could be found on the battlefield as nurses, seamstresses and cooks. A few even saw combat, such as Mary Ludwig Hays, aka Molly Pitcher, who, according to legend, replaced her incapacitated husband at a cannon at the Battle of Monmouth, and Deborah Sampson, who disguised herself as a man. Women played a similar role in the Civil War and other 19th century conflicts. Yet they weren’t allowed to officially serve until the establishment of the Army and Navy Nurse Corps in 1901 and 1908, respectively. The first non-nurse women then enlisted in 1917, when, by working stateside in clerical positions and overseas as Signal Corps operators, they freed up male servicemen for fighting at the World War I front. In 1948, a few weeks before abolishing racial discrimination in the armed forces, President Harry Truman signed a bill allowing women to serve permanently, not just in times of war. The first women were then promoted to general in 1970, and in 1976 females were admitted into the service academies. Today, women make up about 16 percent of the Army, and by 2016 they reportedly will no longer be excluded from ground-combat units.

The military has intervened abroad hundreds of times.

The United States has formally declared war on only five occasions: the War of 1812, the Mexican-American War, the Spanish-American War, World War I and World War II. Yet it has sent its armed forces abroad over 300 times “for other than normal peacetime purposes,” according to a congressional report issued in 2010. The first of those interventions was the Quasi-War against France in 1798-1800, whereas more recent actions have involved Iraq, Afghanistan and the war on terrorism.

For most presidents, a military career predated a political one.

Of the 44 men who have held the office, 31 served in the military in one capacity or another. For some, the experience was short lived and inconsequential. Abraham Lincoln, for example, spent fewer than three months with the Illinois militia, seeing no combat except, as he later deadpanned, against mosquitoes. Others, however, were high-ranking career military men, such as General Ulysses S. Grant, commander of all Union troops at the end of the Civil War, and General Dwight D. Eisenhower, who spearheaded the D-Day invasion of World War II. The only non-officer of the bunch was James Buchanan, a private in the Pennsylvania militia during the War of 1812.

The military is the world’s largest employer.

With about 1.4 million active-duty military personnel, 1.1 million National Guard and reserve personnel and 700,000 civilian personnel, the U.S. Department of Defense employs more people than any other organization in the world. By comparison, the world’s largest corporation, Wal-Mart, has about 2.2 million workers on its payroll. The Department of Defense is also a huge land manager, controlling approximately 30 million acres worldwide, a swath bigger than Pennsylvania.

The United States budgets almost as much money for defense as the rest of the world combined.

In 2013, the United States handed out $619 billion to the military, about as much as the next nine highest-spending countries combined and 37 percent of the worldwide total, according to the Stockholm International Peace Research Institute, which tabulates such numbers annually. Nonetheless, other countries are closing the gap somewhat. While military spending in the United States has dropped recently—it reached a peak of $720 billion in 2010—it has gone up an estimated 170 percent in China, 108 percent in Russia and 118 percent in Saudi Arabia since 2004.