On his return to England, Cornwallis was immediately asked to return to India. One reform that Cornwallis had been unable to achieve was the harmonization of pay and rank between the military forces of the company and those of the Crown. Company officers of a given rank were generally paid better than those of a comparable rank in the Crown forces, and proposals to merge their pay scales were met with resistance that bordered on mutiny. The company directors asked Cornwallis to deal with this; he refused.
After serving for several years as the Master of the Ordnance, he was asked by Prime Minister William Pitt the Younger to serve as Lord Lieutenant of Ireland as well as its Commander-in-Chief after the Irish Rebellion of 1798 broke out. While the rebellion was mostly put down before his arrival, he oversaw the mopping of the remaining pockets of rebellion, and successfully defeated a French invasion intended to foment further rebellious activity. He then worked to secure the passage by the Irish Parliament of the 1800 Act of Union, which joined the Kingdom of Ireland and the Kingdom of Great Britain into the United Kingdom of Great Britain and Ireland. He resigned his posts when the king refused to support Catholic emancipation, which he viewed as a key element for securing an enduring peace in Ireland.
He was then engaged by the king in diplomatic efforts in Europe. Cornwallis led the British diplomatic team whose negotiations with Napoleon resulted in the 1802 Treaty of Amiens, with Cornwallis signing the treaty on behalf of King George.
Return to India
In the years since he left India, the company's reach and control over the country had increased significantly, mainly under the governorship of Lord Mornington. Wellesley had decisively defeated Tipu in 1799, and gained control, direct and indirect, over most of southern India. In 1803 the company came into conflict with the Marathas, and Mornington began extending the company's reach further into the northern territories. His liberal spending and aggressive methods for dealing with the Marathas were not appreciated by the company's directors, and following military setbacks in 1804 and allegations of improprieties, the directors decided to replace him.
On 7 January 1805 Cornwallis was again appointed to the positions of Governor General and Commander-in-Chief of India; he described his After a difficult passage, he reached Madras on 19 July, and on 30 July he resumed his duties. William Hickey wrote that Cornwallis had become "a wreck of what he had been when formerly in Bengal", and another aide noted that "his constitution was less equal to contend against the effects of this climate". In spite of declining health and mental faculties, Cornwallis began a trip by boat to visit army outposts northwest of Calcutta. On the journey he wrote to General Gerard Lake, then commanding the forces in the war with the Marathas, insisting that peace be made. However, he never received Lake's answer. When Cornwallis reached Ghazipur on 27 September, he was too ill to proceed further, and he died there a week later, on 5 October 1805.
|“||This monument, erected by the British inhabitants of Calcutta, attests their sense of those virtues which will live in the remembrance of grateful millions, long after it shall have mouldered into dust.||”|
—Inscription on Cornwallis mausoleum, Ghazipur
Cornwallis's grave at Ghazipur is marked by a mausoleum whose construction was begun in 1809. Memorials were also erected in his honour in Bombay, Madras, and in Saint Paul's Cathedral in London. In Calcutta, when Mornington greatly expanded the government facilities, the Town Hall included a statuary hall. In 1803, a sculpture begun by John Bacon and finished by his son John Bacon, Jr. was erected there in Cornwallis's honour. The sculpture now stands in the Victoria Memorial.