The first military conflict of the U.S. since the Revolutionary War began on this day in 1798, against France, a nation that had been an essential ally in America's fight for independence just 15 years earlier. Ironically, it had been prompted in a way by the French Revolution, when the country overthrew its monarch to found a republic — sound familiar? But the new French government wanted to topple other monarchies in the area and went to war with one of America's biggest trading partners. You'll never guess what country that was.
Great Britain and the U.S. were far from best friends at the time, but they were starting to do business again. The French Republic went to war against the Brits as part of their fight against monarchical rule, and the U.S. declared neutrality. France saw America's financial relationship with their enemy — after they'd provided crucial help in the young country's fight for self-governance, no less — as an affront. Wanting to make trade between the British and Americans untenable, the French began seizing U.S. merchant ships.
Negotiations between the two republics failed to gain any traction, and mutual hostilities got underway. No war was ever officially declared, but both sides captured each other's ships and killed each other's men. The U.S., without a proper navy, managed to take a sizeable piece out of the French fighting force, but was also heavily bruised. Eventually, the two sides agreed to stop fighting in 1800. The Americans were once again free to commence trade with both Britain and France.