quality:corruption
War in Europe

After George's recovery, his popularity, and that of Pitt, continued to increase at the expense of Fox and the Prince of Wales. His humane and understanding treatment of two insane assailants, Margaret Nicholson in 1786 and John Frith in 1790, contributed to his popularity. James Hadfield 's failed attempt to shoot George in the Theatre Royal, Drury Lane, on 15 May 1800 was not political in origin but motivated by the apocalyptic delusions of Hadfield and Bannister Truelock. George seemed unperturbed by the incident, so much so that he fell asleep in the interval.

The French Revolution of 1789, in which the French monarchy had been overthrown, worried many British landowners. France declared war on Great Britain in 1793; in response to the crisis, George allowed Pitt to increase taxes, raise armies, and suspend the right of habeas corpus. Pitt prosecuted British radicals for treason in 1794, and in October 1795, crowds attacked George's carriage on his way to opening Parliament, demanding an end to the war and lower bread prices. In response, Parliament passed the Treason and Seditious Meetings Acts a month later. The First Coalition to oppose revolutionary France, which included Austria, Prussia, and Spain, broke up in 1795 when Prussia and Spain made separate peace with France. The Second Coalition, which included Austria, Russia, and the Ottoman Empire, was defeated in 1800. Only Great Britain was left fighting Napoleon Bonaparte, the First Consul of the French Republic.

A brief lull in hostilities allowed Pitt to concentrate effort on Ireland, where there had been an uprising and attempted French landing in 1798. In 1800, the British and Irish Parliaments passed an Act of Union that took effect on 1 January 1801 and united Great Britain and Ireland into a single state, known as the "United Kingdom of Great Britain and Ireland". George used the opportunity to abandon the title "king of France", which English and British sovereigns had maintained since the reign of Edward III. It was suggested that George adopt the title " Emperor of the British Isles ", but he refused. As part of his Irish policy, Pitt planned to remove certain legal disabilities that applied to Roman Catholics. George III claimed that to emancipate Catholics would be to violate his coronation oath, in which sovereigns promise to maintain Protestantism. Faced with opposition to his religious reform policies from both the King and the British public, Pitt threatened to resign. At about the same time, George had a relapse of his previous illness, which he blamed on worry over the Catholic question. On 14 March 1801, Pitt was formally replaced by the Speaker of the House of Commons, Henry Addington. Addington opposed emancipation, instituted annual accounts, abolished income tax and began a programme of disarmament. In October 1801, he made peace with the French, and in 1802 signed the Treaty of Amiens.

George did not consider the peace with France as real; in his view it was an "experiment". The war resumed in 1803, but public opinion distrusted Addington to lead the nation in war, and instead favoured Pitt. An invasion of England by Napoleon seemed imminent, and a massive volunteer movement arose to defend England against the French. George's review of 27,000 volunteers in Hyde Park, London, on 26 and 28 October 1803 and at the height of the invasion scare, attracted an estimated 500,000 spectators on each day. The Times said: "The enthusiasm of the multitude was beyond all expression." A courtier wrote on 13 November that "The King is really prepared to take the field in case of attack, his beds are ready and he can move at half an hour's warning." George wrote to his friend Bishop Hurd, "We are here in daily expectation that Bonaparte will attempt his threatened invasion... Should his troops effect a landing, I shall certainly put myself at the head of mine, and my other armed subjects, to repel them." After Admiral Lord Nelson 's famous naval victory at the Battle of Trafalgar, the possibility of invasion was extinguished.

In 1804, George's recurrent illness returned; after his recovery, Addington resigned and Pitt regained power. Pitt sought to appoint Fox to his ministry, but George refused. Lord Grenville perceived an injustice to Fox, and refused to join the new ministry. Pitt concentrated on forming a coalition with Austria, Russia, and Sweden. This Third Coalition, however, met the same fate as the First and Second Coalitions, collapsing in 1805. The setbacks in Europe took a toll on Pitt's health, and he died in 1806, reopening the question of who should serve in the ministry. Grenville became prime minister, and his " Ministry of All the Talents " included Fox. Grenville pushed through the Slave Trade Act 1807, which passed both houses of Parliament with large majorities. George was conciliatory towards Fox, after being forced to capitulate over his appointment. After Fox's death in September 1806, the King and ministry were in open conflict. To boost recruitment, the ministry proposed a measure in February 1807 whereby Roman Catholics would be allowed to serve in all ranks of the armed forces. George instructed them not only to drop the measure, but also to agree never to set up such a measure again. The ministers agreed to drop the measure then pending, but refused to bind themselves in the future. They were dismissed and replaced by the Duke of Portland, as the nominal prime minister, with actual power being held by the Chancellor of the Exchequer, Spencer Perceval. Parliament was dissolved, and the subsequent election gave the ministry a strong majority in the House of Commons. George III made no further major political decisions during his reign; the replacement of Portland by Perceval in 1809 was of little real significance.