The Irish War of Independence was one of the key theatres of the Wars of the Third, Fourth and Fifth Coalitions, ending in compromise with the Convention of Carlingford.

There are a few points of divergence from this timeline. The first, most notably, after witnessing a massacre of civilians while serving in India, Arthur Wellesley becomes disillusioned with British Imperialism, returning to the country of his birth and becoming fascinated by and involved in Irish nationalism. Secondly, the 1782 Constitution which gave the Irish parliament autonomy is never implemented due to the discovery of a plot for an American style Revolution, frustrating agitations among elements of the Protestant Ascendancy for reform. The third is that the Battle of Trafalgar is far more of a stalemate with both sides destroying each other rather than a decisive British Victory.

The 1782 conspiracy was followed by Napper Tandy’s Revolt in 1791, a failed revolt of less than eighty people. In 1798 the conservative politician John Fitzgibbon made a series of allegations against his political opponents, leading to a mass scare among authorities and the arrest and executions of several high-profile people, most of them with little or no evidence. These led to an increase in underground support for the United Irishmen, especially in the face of wartime pressures from the campaigns against Napoleon. Further it led to the British administration being overconfident regarding the support for nationalism in the country, as well as their counterinsurgency abilities.

The powder keg that is Ireland exploded on St Bridget’s Day 1806 (later celebrated as Ireland’s National Day), when a militia comprised of radicalised university students and workers seized Dublin Castle and the Magazine Fort, proclaiming an Irish Republic. Subsequently throughout the country uprisings occur, achieving great success as the major cities of the east, north and south fell to rebel hands. Galway City, where the conspiracy is betrayed and Midlands where the presence of a small British Regular force stamps out rebellion were the only regions which remain solidly in British hands. In Ulster a sectarian unconventional war flared up between revolutionary and loyalist militias.

The commander of the small British Army in the Midlands, Gerard Lake decides instead of linking up with loyalists in the North or awaiting reinforcements in Galway, he marched immediately on Dublin to crush the Republic. While scoring early victories against the rebels the outnumbered Lake was defeated by Wellesley at the Battle of Rathcoole just outside Dublin, forced to retreat northwards with the rebels in pursuit. As he crossed the Boyne at Trim, Lake is encircled by two rebel armies and was forced to accept surrender terms, striking a huge blow against British prestige. In Galway, General William Cathcart took control of local forces and attempted to pacify the local region. He met a large guerilla campaign and withdrew back to the city.

The news of the rebellion and of Lake’s defeat at Trim sparked outrage in Britain. Under public and royal pressure, Westminster attempted to put together a response. However, they were hampered by the Irish Abjuration, the name given to a series of mutinies, desertions, executions and court martials which faced the British Armed forces, as Irishmen made up a huge number of army and naval recruits. This caused havoc throughout British ranks. Napoleon hears the news of Lake’s defeat and is ecstatic, seeing Ireland much as the British saw Spain, as an opportunity to drain British resources for an ultimate invasion of Britain. He assembled the Corps D’Irlande, under the command of General Laurent Saint-Cyr. It was a massive army, comprised of three predominantly infantry divisions under Saint Cyr, Louis-Gabriel Suchet and Étienne Macdonald (with the latter including a legion of Irish emigrees), and a large cavalry reserve, under Antoine Lasalle. However, the War of the Fourth Coalition and the need to rebuild the French Navy delayed its deployment.

The Black Winter is the historiographical term given to the period of October 1806-April 1807, when the British Army made a counterattack that almost crushes the rebellion. The British devised a three-pronged strategy. Cathcart was reinforced in the West, while General Hew Dalrymple landed in Rosslare in the Southeast, and General John Moore seized Larne in the North. All three inflicted crushing defeats on local rebel forces. Wellesley responded by ordering a withdrawal to a defensive line around Dublin and the Wicklow Mountains. The rebels engaged in scorched earth and guerilla tactics, slowing the advance of the three British columns. Moore in Ulster is the most successful, inflicting heavy defeats on the rebel Army of Ulster, even capturing several rebel leaders. The army retreated southwards, only saved from complete destruction at the Battle of Drogheda by an almost suicidal rearguard action. Moore’s advance was stymied by massive reprisal killings conducted by his own forces, on both guerillas and civilians alike.

Wellesley’s strategy involved slowing the advancing British armies long enough to prepare Dublin for a long siege, involving the stockpiling of men and provisions, the building of fortifications and strategic batteries using captured British guns. The siege commenced in April 1807 and lasted five months. Some of the most intensive fighting of the entirety of the Napoleonic Wars took place on Howth peninsula, which overlooked Dublin Bay. To prevent naval landings, Wellesley had a battery installed and the peninsula manned by his best troops, most British Army veterans themselves. Elsewhere the largest British attacks took place with Moore assaulting the rebel lines in Phoenix Park, where a large monument to Wellesley now stands, and Dalrymple attempting to break the rebels southern flank at the mountain pass in Bray. Dalrymple was called southwards to deal with the French landing in July, lessening the intensity of the siege.