The burning of Washington took place in August 1814.
The United States had declared war on Great Britain for a variety of reasons. Although in practice the US was no match for the British Empire, the British were busy with Napoleon in Europe and could send very few troops to North America.
So the plan was to attack Canada while the British were busy in Europe.
But things went wrong: in 1814, the coalition of Britain, Russia, Prussia, Spain and Austria crushed Napoleon and his allies and won the war.
Britain now had thousands upon thousands of troops freed up to fight in North America against the US. During a campaign known as the "Chesapeake campaign", 4000 British troops under the command of General Ross landed on the west coast in mid-August.
By the 24th of August, the British reached a village called Bladensburg a few miles away from the city of Washington itself. Waiting at Bladensburg to meet the 4000 British troops was an American commander named Winder with over 5000 militia.
Despite having the numerical advantage, the Battle of Bladensburg was a stupendous British victory due to two main factors:
1. Winder's force was comprised of militia - civilian soldiers - which turned out to be no match for the British regulars.
2. Despite having time and knowledge of the British advance, the Americans failed to build and kind of fortifications, and they didn't even choose to place troops in Bladensburg itself, which would have bogged down Ross's British troops. Winder decided to meet the British in open combat - a fatal error, considering that they were European line infantry which basically fought in fields on a regular basis.
Long story short, when the American militia saw the British bayonets coming at them, they turned and ran. The only kind of resistance was put up by 400 American marines, but they soon fell to the British onslaught.
The battle gave rise to the famous poem "Bladensburg Races" that heralds the incident of American militia literally racing through the streets, trying to escape from the advancing redcoats.
With Bladensburg in British hands and the American army on the run, Ross's troops entered Washington unopposed.
As vengance for the American attack on York (Toronto) in 1813, the British burnt not only the Whitehouse but the Treasury, Library of Congress and the remmenants of the Washington Naval Yard (American militia had burnt the ships to prevent capture).
The "occupation" of Washington lasted 26 hours. Seeing that the damage had been done, the British returned to their ships and sailed away.
So, a little summary:
- British land and march to Washington
- Americans defeated at Bladensburg, Washington left defenseless
- British burn US federal buildings
- British leave
PS: It was hardly a "tragedy", the Americans provoked the British into burning the city... Don't dish it out if you can't take it as well, eh.