Although he started his military career fighting for the English at the behest of his father, Robert would eventually become the first King of Scotland following the occupation of Edward I. King Robert I is most famous for his impressive victory at the Battle of Bannockburn (contrary to popular belief, nothing to do with burning his trousers or 'bannocks') in 1314.
The Scottish won Bannockburn quite decisively. Despite being outnumbered more than three to one by the better equipped English forces, the battle was won in under two days and with the Scottish forces taking minimal losses, counting only two knights among those killed. So crushed were the English by their defeat at Bannockburn that most of their forces were routed and fled in various directions, only to be killed by farmers or militia parties as they attempted to make for the border. In the end, of the 16,000 men fielded by the English roughly 11,000 were killed.
Robert the Bruce would go on to sign the Declaration of Arbroath, a letter that would be sent to the then Pope John XXII, that would seal Scotland's fate as an independent nation and was the inspiration for similar documents throughout history, including the American Declaration of Independance.
All in all, Robert the Bruce was a brilliant King, powerful warrior and all-round decent guy.That is, if you discount that whole 'fighting for the English' thing he had at the start. But, hey. Nobody's perfect!
Quite mis-portrayed in the feature film 'Braveheart' as a weasely coward, in reality Robert the Bruce was a formidable warrior and great leader of men. On the first day of Bannockburn he entered into a duel with an enemy lieutenant by the name of Henry de Bohun mounted on a small palfrey, wearing no armour and carrying only his favourite battleaxe, compared to de Bohun who was riding his warhorse, wearing full battle armour and wielding a lance. De Bohun charged at Bruce, who waited until the last second before gracefully manoeuvring the horse out of the way, standing up in his stirrups and swinging his axe at de Bohun's head with enough force to cleave his head and helmet clean in two and shatter the axe's handle. When asked later about the enormous risk the King had taken in such a bout, Bruce thought nothing of it save that he expressed remorse over breaking the handle of his favourite axe.