By this point his health was very poor - he suffered from both tuberculosis and kidney failure, and he returned to England in an attempt to restore his health, where he learnt he had been appointed to command the force sent up the St. Lawrence River to attack Quebec, with the temporary rank of Major-General for that campaign only. The initial plan to attack Quebec involved three separate forces sent towards the city, with the intention that they would meet at the city, but when Wolfe reached Quebec (25 June 1759), he found that only his force was present, leaving him outnumbered by the French defenders, although his troops were of a much higher quality. His opponent, the Marquis de Montcalm, was an able general, and Quebec itself was a natural fortress, protected by cliffs and gorges, and Wolfe soon found his siege becalmed in front of the city. By August 1759, he was convinced that he was dying, and this may explain why he took the gamble he did. Quebec stood on the north bank of the St. Lawrence River, with high cliffs guarding the western approach via the Plains of Abraham. The French had split their garrison, with the best troops posted eight miles west of the city, and only a very thin guard on the cliff top. On the morning of 13 September 1759, Wolfe crossed the river and climbed the cliffs using a narrow path leading up from a cove, guarded by fifty men, all but one of whom were asleep. Within two hours, he had a force of 4828 men on top of the cliffs, and was even able to get some artillery up the cliffs.
The French were caught completely by surprise. Montcalm himself, investigating a lack of news from the west, discovered the British troops, and made a disastrous blunder. Certain that Wolfe could only have a token force at the cliff tops, he refused to wait two hours for the troops from the west, but instead attacked Wolfe with the garrison of Quebec. Despite outnumbering Wolfe's troops, the French were much less experiences, with a large number of local militia, and the battle was over very quickly. The French advanced towards the British lines, who held their fire until the French were close enough, before letting off a volley that shattered the French line. The Battle of the Plains of Abraham soon turned into a rout, and the French army collapsed, leaving Quebec vulnerable. The city surrendered on 18 September. Both Wolfe and Montcalm were killed in the battle, both surviving to know the result of the battle. The nature of the battle, and his death at the moment of victory, made Wolfe a national hero. News of his death was received with mourning across Britain, and he has a monument in Westminster Abbey. However, if Montcalm had not blundered, Wolfe would have been crushed between two forces, and his reputation would be very different.