The siege of Enniskillen takes place at Enniskillen in Fermanagh, present day Northern Ireland, in 1594 and 1595, during the Nine Years’ War. In February 1594, the English had captured Enniskillen Castle from the Irish after a waterborne assault and massacred the defenders after they surrendered. From May 1594, an Irish army under Hugh Maguire and Cormac MacBaron O’Neill besiege the English garrison in the castle, and in August they defeat an English relief force. A second relief force is allowed to resupply the garrison, but the castle remains cut off. Eventually, in May 1595, the English garrison surrenders to the Irish and are then massacred.

In 1593, Hugh Maguire, Chief of the Name and Lord of Fermanagh, had objected to the behaviour of the newly-appointed English Crown sheriff Humphrey Willis. As he had done before being expelled by Hugh Roe O’Donnell from Tyrconnell in 1592, Willis is cattle raiding and plundering throughout Clan Maguire territory. Maguire is not strong enough to resist the sheriff, but after receiving reinforcements from Hugh O’Neill, Earl of Tyrone, Maguire expels Willis. In May and June 1593, Maguire and Brian Oge O’Rourke of West Breifne raid lands held by the English Lord President of Connaught, Richard Bingham. They destroy the town around Ballymote Castle. This is part of a proxy war waged to distract the Crown while Tyrone strengthens his position in Ulster. As hoped for, the Crown responds by sending an army under Sir Henry Bagenal and Gaelic leader Hugh O’Neill, Earl of Tyrone (outwardly still loyal to the Crown), who defeat Maguire’s force at the Battle of Belleek in October 1593. However, Maguire’s main force remains unscathed.

On May 17, 1594, now acting with the covert support of Tyrone, Hugh Maguire and Cormac MacBaron O’Neill lay siege to Enniskillen which is now isolated in hostile country. Their army consists of 1,400 foot soldiers and 600 horsemen. It quickly grows with support arriving from Hugh Roe O’Donnell. The English commander, James Eccarsall, has only 50 foot soldiers and 24 horsemen to defend the castle, along with some light artillery. Eccarsall launches a sortie by boat but has to retreat under heavy fire. Irish fortifications cut off access by river and the castle is attacked nightly. Many of the garrison fall sick due to food shortages and exhaustion brought on by incessant skirmishing with the Irish.

On August 7, Maguire and his allies defeat an English relief force for Enniskillen at the Battle of the Ford of the Biscuits. A second relief force commanded by the Lord Deputy William Russell is sent by another route. Although it is not attacked by the Irish, none of Russell’s scouts or messengers reach the castle nor return. Russell relieves the beleaguered garrison by August 30 with six months supplies, then withdraws. Following this, there is a truce, but “subterfuge and deception were the hallmarks of this stage of the war.”