On the 2nd September 1898, General Sir Herbert Kitchener lead his army, made up of Regular British regiments and mixed Sudanese/Egyptian regiments into action against the army of Abdullah al-Taashi, the successor to the self-proclaimed Mahdi, Muhammad Ahmad. Ostensibly the Battle the of Omdurman, as it became known was fought to help the Egyptian state reconquer the Sudan, though Kitchener was seeking revenge for the death of General Charles Gordon in Khartoum in 1885.
The battle has become famous/infamous for a number of reasons:
It demonstrated how a highly disciplined army, armed with modern rifles, artillery and machines guns could destroy an army twice its size but armed with obsolete weapons with minimal casualties. 16,000 dervishes attacked the British position, mainly armed with old rifles and spears, not one attacker reached within 50m of the British and suffered 4,000 casualties too artillery fire and then heavy volley fire and Maxim guns.
The battle was the first time that the Mark IV hollow point bullet, made in the arsenal in Dum Dum was used in a major battle. It was an expanding bullet and the units that used it considered it a great success though they caused dreadful wounds.
After a few incidences of wounded dervishes attacking British troops, Kitchener ordered all of the wounded the be killed and this brutal attack dogged him for the rest of his life, even Winston Churchill agreed he had gone to far.
Kitchener was anxious to occupy Omdurman before the remaining Mahdist forces could withdraw there. He advanced his army on the city, arranging them in separate columns for the attack. The British light cavalry regiment, the 21st Lancers, was sent ahead to clear the plain to Omdurman. They had a tough time of it. The 400-strong regiment attacked what they thought were only a few hundred dervishes, but in fact there were 2,500 infantry hidden behind them in a depression. After a fierce clash, the Lancers drove them back (resulting in three Victoria Crosses being awarded to Lancers who helped rescue wounded comrades)
The correspondent from Reuter describes the action:
Omdurman, September 4 (via Nasri, Monday)
There has been such a pressure of daily work that the great incident of the Battle of Omdurman has probably received less attention than it merited. This was the famous charge of the 21st Lancers against enormous odds.
Colonel Martin’s orders were to prevent the broken enemy from returning to Omdurman, five miles away from the filed of Battle. The 21st Lancers unexpectedly came upon the enemy’s reserve who were 2000 strong, but whose exact strength could not ascertained owing to the nature of the ground.
The cavalry were then in form of troops. They deployed into line for the attack and charged. When they were within thirty yards of the entrenchments they found the enemy ensconced in a nulla and concealed by a depression of the ground.
The Lancers wild with excitement and coming on at full gallop for the attack, had not a single moment for hesitation. They charged gallantly home, the brunt falling on No.2 squadron, who absolutely had to hack their way through the enemy twenty deep, exposed to a withering infantry fire.
They struggled through, but every man who fell was immediately hacked to pieces by the swords of the fanatic foe.
The men of the British cavalry rallied, bleeding, on the far side of the lanes which they had cut for themselves in the enemy’s ranks and with admirable fortitude they re-formed as coolly as if they had been on parade.
One corporal, who was covered in blood, and reeling in his saddle, when ordered to fall out shouted , waving his bent lance- “Never! Form up No.2” meaning his squadron.
Then it was that young Grenfell was missed for the first time. Lieutenant de Montmorency, with Corporal Swarback dashed out to effect, if possible, the rescue of his body. They were immediately joined by Captain Kenna.
With their revolver fire the two officers kept the enemy forty yards away, and would have secured Lieutenant Grenfall’s body if the horse upon which it was placed had not shied with its burden.
Then seeing that a second charge would be futile, colonel Martin dismounted his men and with magazine and carbine fire drove the enemy steadily into the zone of the Anglo-Egyptian infantry fire, the Lancers having accomplished their object by covering the enemy line of retirement though at the cost of heavy casualties. This maiden charge of the 21st Lancers is regarded as an extremely brilliant affair. 
Of less than 400 men involved in the charge 70 were killed and wounded and the regiment won three Victoria Crosses. These three were Private Thomas Byrne, Lieutenant Raymond de Montmorency and Captain Paul Kenna.
Winston Churchill was present at the battle and he rode with the 21st Lancers.
 The Citizen 10th September 1898.