Seeking a symbol around which to rally, the first sepoys to rebel sought to reinstate the power of the Mughal Empire, which had ruled much of the Indian subcontinent in the previous centuries.

Firstly, large numbers of rebels were committed to the defence of a single fixed point, perhaps to the detriment of their prospects elsewhere, and their defeat at Delhi was thus a very major military setback.

Secondly, the British recapture of Delhi and the refusal of the aged Mughal Emperor Bahadur Shah II to continue the struggle deprived the rebellion of much of its national character.

The cartridges for this were widely believed to be greased with a mixture of cow and pig fat, and to bite them open when loading the rifle (as required by the drill books) would defile both Hindu and Muslim soldiers.

They were hastily court martialled, and on 9 May 1857 they were sentenced to long periods of imprisonment and were paraded in irons before the British and Bengal regiments in the garrison.

The Bengal regiments broke into rebellion on Sunday, when European troops customarily attended evening church parade without arms.

Due to the increasingly hot summer weather, the church services on 10 May took place half an hour later than on previous weeks, and when the outbreak occurred, the British troops had not yet left their barracks and could quickly be mustered and armed.

[6]: 97–8  In the city meanwhile nine British officers from the Ordnance Corps, led by George Willoughby were conducting the Defence of the Magazine, which contained artillery, stocks of firearms and ammunition.

Rumours and envoys from the rebels spread the tidings fast and precipitated widespread rebellions and uprisings, but the Company learned of the events at Delhi even more quickly, thanks to the telegraph.

[9]: 475  The Meerut force was led by Brigadier Archdale Wilson, who had conspicuously failed to prevent the rebel sepoys' move to Delhi on 11 May.

This was a senseless act, as it condemned the besiegers (and all their sick and wounded and noncombatants) to live in tents through the hot weather and monsoon rain seasons.

Fortunately for the besiegers, a canal ran from the Yamuna west of their encampments, protecting the rear of their camp and also providing drinking water.

South of it was a maze of villages and walled gardens, called the Subzi Mundi, in which the rebel forces could gather before launching attacks on the British right.

The majority of no less than ten regiments of cavalry and fifteen of infantry of the Bengal Army rebelled and made their way to Delhi during June and July,[10] along with large numbers of irregulars, mainly Muslim mujahaddin.

Although Wilson made efforts to clear the unburied corpses and other refuse from the ridge and encampment and reorganise the outposts and reliefs, he himself was scarcely capable of exercising command, and in every letter he wrote, he complained of his exhaustion and prostration.

Also, the rulers of the states of Patiala, Jhind and Nabha were induced to support the East India Company, sending contingents of their armies to secure the lines of communication between the besiegers and the Punjab.

[12] The first reinforcements to arrive at Delhi, the Corps of Guides, made an epic forced march of several hundred miles through the hottest season of the year, which also coincided with the month of Ramadan, during which their Muslim soldiers could neither eat nor drink during the day.

The major force dispatched from the Punjab to Delhi were a "Flying Column" of 4,200 men under Brigadier John Nicholson and a siege train.

Although the monsoon had broken and the roads and fields were flooded, Nicholson drove his force to make a rapid march and gained an easy victory, raising European morale and lowering that of the rebels.

[14] Wilson's chief Engineer Officer, Richard Baird Smith, had drawn up a plan to breach the city walls and make an assault.

[9]: 478  A third battery of six 18-pounder guns and 12 Coehorn mortars was set up near the old Custom House less than 200 yards (180 m) from the city walls, and opened fire against the Water Bastion near the Yamuna next day.

By this time also, the rebels had become depressed through lack of supplies and money and by defeatist rumours which were spread by agents and spies organised by William Hodson.

The future Field Marshal Lord Roberts, then a junior staff officer, recorded their composition: Detachments of the 60th Rifles, totalling 200, preceded all the columns, as skirmishers.

[9]: 479 There was also a cavalry brigade in reserve under James Hope Grant, which probably consisted of: The first three columns, under Nicholson's overall command, gathered in and behind a building known as the Khudsia Bagh, a former summer residence of the Mughal Kings, about a quarter of a mile from the north walls.

The rebels followed up, capturing four guns from the Kashmiri troops, and threatened to attack the British camp, which had been emptied of its guards to form the assault force.

Rebel soldiers held most of the flat rooftops and walled compounds, and guns mounted on the bastion fired grapeshot down the lanes between the houses.

However, the rebel sepoy regiments had become discouraged by their defeats and lack of food, while the irregular mujahhadin defended their fortified compounds with great determination, but could not be organised to make a coordinated counter-attack.

After the siege, many civilians were subsequently expelled from the city to makeshift camps in the nearby countryside, as there was no way of feeding them until order was restored to the entire area.

In many cases, the officers of the "Queen's" Army were inclined to be lenient, but East India Company officials such as Theophilus Metcalfe were vengeful.

Although he was urged to accompany Bakht Khan and rally more troops, the aged Emperor was persuaded that the British were seeking vengeance only against the sepoys they regarded as mutineers, and he would be spared.