Between 1651 and 1986, a vicious and harrowing war was fought between the Netherlands and the Isles of Scilly, which is located in Great Britain. That's 335 years of war, except that it wasn't 'vicious' or 'harrowing' in the least, it was actually a war that didn't see a single drop of blood spilled and was basically only a war on paper, if at all.
The war is said to have been 'fought' for 335 years without a single shot being fired and without a single casualty, making it one of the world's longest and most bloodless wars ever.
The origins of this war can be traced back to the Second English Civil War, but a little background is required. After Elizabeth I died, the crown passed to her cousin, James Stuart and for the first time, England, Ireland, and Scotland were united under one monarch. This obviously presented it's own problems, and soon enough, outright rebellion by the Irish against the English and Scottish settlers led to a division of power. The Royalists supported the king and his right to rule, while the Parliamentarians wanted the king gone.
This is where the Netherlands came in. They had decided to support the Parliamentarians, which rightly pissed the Royalists off no end.
The Royalists then attacked and raided pretty much every Dutch ship that came into the English Channel.
However, the Royalists had nothing close to the strength required to fend off these forces, and slowly they retreated to their last stronghold, the Isles of Scilly. Since the Dutch had lost considerable forces to the Royalists, they sent 12 warships there to demand reparations for all the ships and goods taken. The Royalists refused however, further enraging the Dutch.
The Dutch finally declared war on the Isles of Scilly, a Royalist stronghold, in 1651. The Royalists soon surrendered to the Parliamentarians however, so the Dutch had no one to ask for reparations from, and simply went back without declaring the war over.
Over the next 300 plus years, people pretty much forgot that this state of war was still in existence (yup, they actually FORGOT a war was still going on), that is until one historian dug up a little trove of information about it in 1986. He enquired at London’s Dutch embassy, who found the documents supporting this claim, and were probably dumbfounded and more than a little aghast.