The Abyssinia-British War was not an expansionist war but a rescue mission. The Emperor Tewodros II was holding European hostages.
In 1862, he had made a request to the British for weapons and military experts.
As a Coptic Christian regularly engaged in warfare with Muslim neighbors, he wanted British support and expertise both to help him control his own kingdom and to block the spread of Islam in the Horn of Africa.
He wrote a letter to Queen Victoria asking for help, but, for reasons unknown, the letter remained unanswered.
Angered by the lack of response, Emperor Tewodros was further infuriated when he found out that the British Consul, Captain Charles Cameron, had just returned back to Abyssinia after a visit to neighboring Egypt, one of Abyssinia's enemies.
The emperor decided to hold Captain Cameron and others hostage until he received a reply to his letter.
The Liberal Government in Britain was reluctant to get involved. But letters from Captain Cameron to the British press, and the fact that British women and children were numbered among the hostages, gave the matter high profile.
The Abyssinian dispute became an issue in the British general election, with the Tory Party under Lord Derby and Benjamin Disraeli committing itself to a rescue mission should they be elected.
The expedition sets out with Sir Robert Napier, at the time serving as Commander-in-Chief of the Bombay Army, was appointed commander of an Abyssinian expedition by the incoming government.
He immediately set about organising a force that could land in Abyssinia, march deep into the interior of the continent, keep supply lines open, and fight and win a battle at the mountain fortress of Magdala.
He estimated that he would require at least 12,000 soldiers. In the end, 13,000 troops - plus 8,000 auxiliary workers, thousands of mules, hundreds of camels, and 44 Indian elephants - were despatched from Bombay on the 21 December 1867.
It took them just over two weeks to reach Annesley Bay on the east coast of Africa, where they established their main base.
Though well-sheltered, the water in the bay was shallow, entailing the construction of two 300m-long jetties.
A railway was built to transport supplies some 10km. American-designed condensers were used to produce 120 gallons of fresh water from seawater each day.
Time was critical. The whole expedition had to complete its mission by June in order to miss the torrential summer rains that would terminate all campaigning.
In addition, the British were aware that Emperor Tewodros was gathering his forces in the seemingly impregnable fortress at Magdala, some 400 miles to the south.
With a sizeable army and some heavy artillery, Emperor Tewodros was a potentially formidable foe.
The British forces commenced their march to the interior on 26 January.
Units of the 3rd Dragoon Guards and the 26th Regiment of Foot were left at Annesley Bay to guard the bridgehead, while the 4th, 33rd, and the 45th Regiments of Foot - together with a number of Indian regiments and support units - constituted the main assault force.
Napier travelled with the troops and held meetings on the way with various local chiefs, making treaties to protect his lines of communication and secure additional supplies.
The arduous journey took nearly two and half months to complete. The road was treacherous: miles of sun-baked plains, scrubland, and farmlands before finally meeting with the hills and mountains the army would have to cross to reach Magdala.
The mountains presented serious logistical problems. The trails were at times non-existent, and ropes and pulleys had to be employed to move stores and equipment.
Heavy rain made the challenge even greater, and over time, the force was reduced in number as units were detached to guard the route and essential supply-line stretching back to the coast.
On the 24 March, the force entered Dildi. From here, they could see the fortress of Magdala on the horizon.
Although only 25 miles by a direct route, the mountains would impose a tortuous route of some 60 miles in total, passing through some of the most inhospitable mountain country imaginable. Deep ravines and precipices ensured that the expedition advanced at a very slow pace.
As the British column approached Magdala, Emperor Tewodros attempted to seize the initiative with a daring raid.
Thousands of Abyssinians rushed down the mountain to engage the British hand-to-hand. The 4th King's Own Regiment, at the head of the column, formed into skirmish order and opened fire as the Abyssinians hurtled towards the baggage train.
Their firepower, at close range with new breech-loading Snider rifles, was devastating, completely shattering the musket- and spear-armed Abyssinian forces.
Over 500 Abyssinians were killed outright and many more were wounded in an engagement that lasted an hour and a half. The British and Indian troops suffered barely a casualty.
Having lost the initiative, Tewodros had no option but to retreat into the fortress itself and await the final assault.
He attempted to sue for peace and did release the hostages, but Napier's attitude hardened towards him with the discovery of a mound of mutilated corpses at the base of the cliff surrounding the fort.
After an opening bombardment by British mountain guns, the infantry provided covering fire for the engineers to approach the gates.
A storming party of engineers arrived at the gate under fire, only to realise that they had forgotten their explosives.
In the confusion, a soldier of the 33rd Regiment found an alternative entrance. Enough soldiers managed to climb over a wall that they were able to overpower the defenders at the gate and allow the main assault force into the fortress.
The body of Emperor Tewodros was found nearby. He had shot himself with a pistol that had, it is claimed, been a present from Queen Victoria.