In 1941 Britain attacked what was then the Italian colony of Eritrea, as part of the UK’s East Africa campaign during the Second World War. The 4th Indian Division played a major role in this campaign. This culminated in the Battle of Keren.
Wikipedia gives this description of what took place and how it led to the liberation of Asmara on 1st April 1941. The photographs below were meant to show that moment, but I have been reliably informed that the troops are not Indian, but Sudanese, who also participated in this offensive.
Battle of Keren
On 12 January, Aosta had sent a regiment of the 65th Infantry Division Granatieri di Savoia (General Amedeo Liberati) and three colonial brigades to Keren.
The 4th and 5th Indian Infantry divisions advanced eastwards from Agordat into the rolling countryside, which gradually increased in elevation towards the Keren Plateau, through the Ascidira Valley.
There was an escarpment on the left and a spur rising to 6,000 ft (1,800 m) on the right of the road and the Italians were dug in on heights which dominated the massifs, ravines and mountains.
The defensive positions had been surveyed before the war and chosen as the main defensive position to guard Asmara and the Eritrean highlands from an invasion from Sudan.
On 15 March, after several days of bombing, the 4th Indian Division attacked on the north and west side of the road to capture ground on the left flank, ready for the 5th Indian Division to attack on the east side.
The Indians met a determined defence and made limited progress but during the night the 5th Indian Division captured Fort Dologorodoc, 1,475 ft (450 m) above the valley. The Granatieri di Savoia and Alpini counter-attacked Dologorodoc seven times from 18 to 22 March but the attacks were costly failures.
Wavell flew to Keren to assess the situation and on 15 March, watched with Platt as the Indians made a frontal attack up the road, ignoring the high ground on either side and broke through.
Early on 27 March, Keren was captured after a battle lasting 53 days, for a British and Commonwealth loss of 536 men killed and 3,229 wounded; Italian losses were 3,000 Italian and 9,000 Ascari killed and about 21,000 wounded.
The Italians conducted a fighting withdrawal under air attack to Ad Teclesan, in a narrow valley on the Keren–Asmara road, the last defensible position before Asmara.
The defeat at Keren had shattered the morale of the Italian forces and when the British attacked early on 31 March, the position fell and 460 Italian prisoners and 67 guns were taken; Asmara was declared an open town the next day and the British entered unopposed.
You can watch a Pathe News film made at the time which charts this campaign.
Britain was left administering Eritrea after the war was concluded.