Today I'm going to veer a little off track. Up until now I've kept my stories to the period of modern mechanical warfare, say after 1900. There are many good reasons for it, not least its of interest to you, and its easier to find sources.
However last Friday (the 12th of September) is the anniversary of a battle, that is almost unknown in the West. The soldier who mentioned where I could read it last year stated "[...]made the 300 Spartans look like a bunch of girl guides." He's not wrong either. So lets cast our minds back to September 1897.

Regions of Asia, from Afghanistan down through northern Pakistan, have always been a problem for military forces. Go as far back as you like and you'll find tales of armies and governments failing to control the border areas by force. In the late 1800's it was no exception, the area was called the Northwest Frontier, and was still causing issues as late as the 1930's (and it had a small part in tank development that I hope to cover at a later date). The Tirah Valley stretches south from the Khyber Pass, and as such is a main trade route. In 1897 the local Afridi tribesmen began attacking merchant caravans travelling this route. To stop these attacks the 36th Sikh Regiment was deployed to the area. At the base of the valley ran the Samana mountain range. On top of this were two British built two forts, Lockhart and Gulistan. These forts were several miles apart and separated by bad terrain. Each fort had roughly a regiment (200 at Gulistan and 300 at Lockhart) in it. As they lacked the ability to communicate a signals fort was built in between. This fort was called Saragarhi. A tower in the middle of the fort housed a heliograph to communicate with its neighbours.
36th Sikh's
Through out August some minor skirmishing happened with local tribesmen taking the forts under fire once or twice. On one occasion a large attack was launched against Fort Gulistan on the third of September. A relief column left Fort Lockhart, but by the time the column had arrived the attack was defeated. As it made its way back a small detachment of men was left to reinforce Fort Saragarhi.

On September the 12th the local tribesmen were back, reinforced themselves they numbered between 10,000 and 14,000 men. To sever communication between the two forts they launched an all out attack on Saragarhi. Inside the fort were 21 men, carrying nothing more than their personal weapons. At this time it would have been a lever action rifle, the Martini Henry (the gun from the film Zulu).
Local Tribesmen from the region
Upon seeing the horde approach the regiment's commanding officer gave permission for the 21 defenders to retreat. However if they retreated it would mean that the route between the two forts would be severed, and Fort Gulistan would have been cut off. To a man, all 21 soldiers volunteered to hold their position to the last.

Havildar Ishar Singh was in command, he and 19 of his men took up firing positions around the wooden gate. One soldier was dispatched to the heliograph tower to maintain communications. At 0900 the first assault began. Havildar Ishar let the initial rush come within 300 yards before ordering his men to open fire. They then kept up a constant, steady and deadly volume of rifle fire. The Sikh's inside kept up a withering hail of gunshots that kept the horde of tribesmen from closing with the fort.

The stiffness of the defence held despite some casualties from return fire. The man up in the heliograph tower kept to his duties despite his exposed position. After a long and protracted gun battle the attackers fell back, but tried a new tactic. They called for surrender making lavish promises including survival. The Sikhs refused.
At Fort Lockhart a relief column was formed and moved out. However by now the attackers had taken up blocking positions and the relief column was forced to turn back.
Saragarhi after the attack
Throughout the morning attacks continued, each one forced back by the defenders. By midday around seven separate assaults had been bloodily repulsed. However the strain was beginning to tell on the defenders and only ten men remained including the injured Havildar Singh. By 1400 the defenders were almost out of ammunition. At 1500 the attackers tried a new tactic, they set fire to the scrub to create a smoke screen, under the cover of the smoke they began to get into some dead ground on the side of the fort and managed to create a breach.
Fort Lockhart was higher than Saragarhi and could see what was happening, and flashed a warning to the defenders. Two men and the wounded Havildar Ishar moved to cover the breach. Utterly out of ammo now the three of them fixed bayonets and charged the attackers whom had made it through. But overwhelming numbers meant it was hopeless. With the manpower thinned at the main gate the attackers mounted a final assault that forced through the weakened line.
Havildar Ishar tried to hold his ground while the rest of his men retreated to an inner defensive line however the surge of attackers swept over them. One man whom had been wounded earlier in the fight was holding the Guardroom. He managed to fight off four attackers, despite bleeding heavily from his wounds. Rather than lose any more men the attackers set fire to the guardroom.

By 1530 there remained only one defender. Sepoy Gurmukh Singh had been stationed throughout that day on the heliograph tower communicating with Fort Lockhart. His final signal was asking for permission to quit his post, take up his rifle and attack! He was instantly given permission. From Fort Lockhart they watched as Sepoy Gurmukh packed the fragile heliograph into its case, picked up his rifle and launched himself at the enemy. They saw him kill about 20 in his final charge.

The days fighting had brought the rest of the regiment the time it needed. Although the tribesmen attacked Fort Gulistan they'd been delayed too long and a larger relief force arrived, linked up with Fort Lockhart and then broke the siege of Fort Gulistan defeating the attackers.
All 21 defenders (Full list of names and numbers) were given the Indian Order of Merit, the Indian equivalent of the Victoria Cross.