James Madison's stature in history was a lot greater than his actual stature. He was our shortest president….but he was also the only president who literally entered battle while he was president. Granted, this was because the British were attacking Washington, D.C., but it counts. (Source)
Like a lot of his fellow Founding Fathers, Madison went to law school. Unlike them, he had no intent to actually practice law. Ironically enough, Madison would use his training eventually to make the law, which is basically like being a super-lawyer.
Also like a lot of the Founders, Madison was a member of the powerful and influential planter class. After his graduation from the College of New Jersey (it was later called Princeton), Madison more or less immediately turned to the revolutionary movement. He was already managing the local Orange County militia by 1774, and next year joined the Virginia militia with the lofty rank of colonel. (Source)
Because he was a small dude—a lot of combat at the time was still settled hand-to-hand—Madison served the revolution as a writer and a politician.
And he was good at it.
He helped George Mason with the Virginia Constitution, inserting special language protecting religious freedoms. He was an early and powerful champion of the concept of separation of church and state, which is that awesome thing that makes sure we aren't all compelled to be the same religion. (Incidentally, based on when the Constitution was written and who was powerful, that religion would have been Anglican.)
Madison's biggest stamp on history comes with that document that everyone claims to be an expert on but so few people have read: the Constitution. Madison created the concept of separation of powers, which is idea of three separate-but-equal branches of government, the legislative, executive, and judicial. He also was a champion for a stronger federal government than there was under the Articles of Confederation. (Source)
This was pretty ironic considering he'd go on to co-found the Democratic-Republican party with Jefferson.
Madison helped ratify the Constitution with his contribution to the Federalist Papers. He, Alexander Hamilton, and John Jay, wrote a series of 85 essays in support of the Constitution, which helped get the public support necessary for ratification. (Source)
Now he's known as the Father of the Constitution, and though he was too modest to accept the title, without him the country would look super-different.
When the Quasi-War first broke out, Madison wasn't part of the administration. His early support of Federalist principles had soured, mostly because he was butting heads with Hamilton. Hamilton's policies, Madison said, mostly helped out rich northerners and hurt everyone else. (Source)
He reacted to the Alien and Sedition Acts by serving as the Robin to Jefferson's Batman. While Jefferson wrote the Kentucky Resolution, Madison wrote the Virginia version, which is much less revolutionary than the other.
Madison would serve under Jefferson as Secretary of State, and later succeed his old mentor as President. Unfortunately for Madison, his term coincided with that of another famous short guy: Napoleon Bonaparte. Eventually, Napoleon's wars sucked in the United States, where it's known as the War of 1812, because people in the 19th century were really boring when it came to naming things.
The British invaded American soil and even burned Washington D.C. to the ground. The most significant American victory, the Battle of New Orleans, happened after the treaty ending the war was signed. The War of 1812 was widely considered a victory for America though, because as bad as the Americans were drubbed, no territory was lost. (Source)
After his two terms as President, Madison retired to his plantation in Virginia. He kept active in his old age, serving as Rector of the University of Virginia. Despite being a slaveowner himself, he was concerned with the ongoing effects of slavery. Rather than embrace the obvious correct answer—stop owning slaves, free everybody, and give them equal rights under the law—he thought returning them to Africa was the best idea.
Close, but no cigar.
He died in 1836, the final Founding Father left standing. Though he was ignored by the people who took over the Democratic-Republican Party, people like Andrew Jackson and Martin Van Buren, history has largely embraced Madison. And we think that's awesome: Madison deserves a big old bear hug from history.