The Siege of Kinsale occurred in 1601-1602 when a Spanish invasion force captured the Irish city of Kinsale with the help of Hugh O'Neill's Catholic rebels, only to be besieged by the English and forced to surrender.
Following the failure of the Spanish Armada in 1588, King Philip II of Spain decided to support Tyrone's Rebellion in Ireland in order to create a new front in the war against England. The 2nd Spanish Armada of 1596 was smashed by storms before it could assist the Irish rebels, and the 3rd Spanish Armada failed a year later for similar reasons.
After Philip II's death in 1598, King Philip III of Spain continued to provide direct support to the Irish, dispatching 6,000 Spanish troops to Ireland in 1601. The majority of the force's veteran soldiers were forced to turn back due to bad weather, but the remaining 4,000 landed at Kinsale and secured the town of Kinsale. The Spaniards allowed the local populace to abandon the cities, which were promptly besieged by Charles Blount's English occupation forces. The Spanish failed to expand their base into the surrounding region and found themselves surrounded, and Donogh O'Brien, 4th Earl of Thomond reinforced the besiegers up to 12,000 troops. However, many of the Irish levies were not suited to winter siege warfare, and only 7,500 men were able to fight. Blount's forces were incapable of surrounding Kinsale, but they seized some higher ground and constantly bombarded the Spanish forces with artillery, while Admiral Richard Leveson's 10-ship fleet cut off the town from the sea. English cavalry harried the surrounding countryside, and the Irish rebels refused to reinforce Kinsale, lest they leave Ulster vulnerable to attack. Spanish reinforcements arrived at Castlehaven and threatened the English camp, and a combined Irish-Spanish attack was planned. The Spanish attempted to organize the Irish into tercio combat formations, repelling an initial English cavalry charge. However, the Irish cavalry mistook the English retreat for a rout and were repulsed by English gunfire. The Irish cavalry charged back into their own ranks, and the English proceeded to attack the disorganized Irishmen and rout them. The Spanish resisted fiercely with their pikes, only to be overcome and hacked to pieces. The remaining Spaniards surrendered in exchange for safe passage back to Spain, unaware that they were to receive reinforcements. This reinforcement fleet promptly turned back to Spain, putting an end to Spanish help in Ireland and to much of the Irish resistance. The remaining Ulster rebels surrendered in 1603, just after the death of Queen Elizabeth I of England.