In 1602 O'Neill destroyed his capital at Dungannon due to the approach of Mountjoy's forces, and withdrew to hide in the woods. In a symbolic gesture Mountjoy smashed the O'Neills' inauguration stone at Tullaghogue. Famine soon hit Ulster as a result of the English scorched earth strategy. O'Neill's uirithe or sub-lords  began to surrender and Rory O'Donnell, Hugh Roe's brother and successor, surrendered on terms at the end of 1602. However, with a secure base in the large and dense forests of Tir Eoghain, O'Neill held out until 30 March 1603, when he surrendered on good terms to Mountjoy, signing the Treaty of Mellifont. Elizabeth I had died on 24 March. Although the war had effectively ended with the signing of the Treaty of Mellifont, its final battles were fought during the English invasion of West Breifne in April 1603, which remained the sole holdout Irish kingdom following O'Neill's capitulation. The kingdom was ruled by Brian Óg O'Rourke, one of the alliance's chief lieutenants and leader of the Irish forces during the Battle of Curlew Pass. He failed to secure any concessions from the treaty as his half-brother Tadhg O'Rourke had fought with the English during the war and was granted lordship of West Breifne in return. Following a twelve-day siege, a force of 3,000 men led by Tadhg, Henry Folliott and Rory O'Donnell eventually brought the area, and thus all of Ireland, under English control on 25 April 1603.
Question: How many years did the conflict last?
Answer: 1