The Siege of Leith occurred in 1560 when an English army was sent to assist the Protestant Scottish forces of Regent Arran in driving out the French garrison of Leith, which was commanded by the Scottish Catholic regent Mary of Guise.
The French garrison of Leith had arrived by invitation in 1548, garrisoning the city in order to protect it from English invasion during the "Rough Wooing". Andre de Montalembert arrived in Leith with 8,000 troops, and the English were forced to withdraw in 1549 due to high troop expenditures. The French continued to strengthen the defenses of Leith in 1559, and Mary of Guise landed an additional 4,000 French troops there. Queen Elizabeth I of England was intimidated by Thomas Howard, 4th Duke of Norfolk into ordering a military response, sending Admiral William Wynter and a fleet of Royal Navy ships into the Firth of Forth. 6,000 English troops under Lord Grey de Wilton marched from Berwick to join up with the rebellious Protestant Scottish lords in ousting the French from Scotland.
The younger, ill-trained English forces were defeated by the professional French forces, with Mary of Guise noticing that many of the soldiers sent to fight at Leith were children; the bishops in England had refused to send grown men to fight. The Catholic lords and priests of England had intentionally deprived Elizabeth's army of proper soldiers and used the defeat to argue for Elizabeth's removal. Elizabeth realized the depth of the conspiracy against her and her dwindling options, and she accepted Mary of Guise's conditions, to consider marrying her nephew, the Duke of Anjou. The siege was called off under the terms of the Treaty of Edinburgh, which replaced Scotland's Auld Alliance with France with a new Anglo-Scottish accord and a peace treaty between England and France.