Cromwellian conquest of Ireland: Oliver Cromwell's New Model Army ended the Siege of Drogheda, took over the town and massacred its garrison.

The Cromwellian conquest of Ireland (1649–1653) was the re-conquest of Ireland by the Commonwealth of England, initially led by Oliver Cromwell. It forms part of the 1641 to 1652 Irish Confederate Wars, and wider 1639 to 1653 Wars of the Three Kingdoms. Modern estimates suggest that during this period, Ireland experienced a demographic loss totalling around 15 to 20% of the pre-1641 population, due to fighting, famine and bubonic plague.

Oliver Cromwell was an English statesman, politician and soldier, widely regarded as one of the most important figures in British history. He came to prominence during the Wars of the Three Kingdoms, initially as a senior commander in the Parliamentarian army and latterly as a politician. A leading advocate of the execution of Charles I in January 1649, which led to the establishment of the Commonwealth of England, Cromwell ruled as Lord Protector from December 1653 until his death.

The New Model Army or New Modelled Army was a standing army formed in 1645 by the Parliamentarians during the First English Civil War, then disbanded after the Stuart Restoration in 1660. It differed from other armies employed in the 1639 to 1653 Wars of the Three Kingdoms in that members were liable for service anywhere in the country, rather than being limited to a single area or garrison. To establish a professional officer corps, the army's leaders were prohibited from having seats in either the House of Lords or House of Commons. This was to encourage their separation from the political or religious factions among the Parliamentarians.

The Siege of Drogheda, 3 to 11 September 1649, took place at the start of the Cromwellian conquest of Ireland. The port of Drogheda was held by a mixed garrison of Irish Catholics and Royalists under the command of Sir Arthur Aston, when it was besieged by English Commonwealth forces under Oliver Cromwell.