In September 1961, the Irish Army under the United Nations flag was engaged in operations against Katanga, a breakaway region in Congo. Some 155 Irish troops were stationed at a little base near Jadotville in order to protect the citizens of the small mining town. But the locals in Jadotville wanted nothing to do with the Irish, believing the U.N. had taken sides in the conflict between the Congolese government and Katanga.
For five days, the 155 Irish fought for their lives against as many as 4,000 mercenaries and rebels who tried to take them captive.
The enemy came at the Irish in the middle of a Catholic Mass. Luckily for the Irish, one of their sentries, Pvt. Billy Ready (seriously, his name was "Ready"), fired the shots that alerted the Irishmen to their enemy. What they saw when they went to their posts was 3,000-5,000 hired guns ready to take down their position – the Irish numbered just 155. The mercs brought with them not only heavy machine guns, but also artillery and heavy mortars. They also had air cover in the form of an armed trainer aircraft. It didn't rattle the Irish one bit, as they later radioed U.N. headquarters:
"We will hold out until our last bullet is spent. Could do with some whiskey."
As far as weapons go, the Irish had only light machine guns and 60 mm mortars to defend their position. But in a testament to warfighting fundamentals, the Irishmen were able to shut down their enemy's mortar and artillery capabilities using just accurate mortars and small arms. It was the pinpoint accuracy of the U.N. troops that would sufficiently level the playing field. This exchange lasted four days. Now, down to 2,000 men, the Katangese asked the Irish for a cease-fire.
Meanwhile, a U.N. relief force of Swedes and Indian Army Gurkhas were making a move on the Katangese positions from the other side. They were held down at a bridgehead on the road from the main U.N. base at Elisabethville and despite inflicting heavy losses on the defending Katanga fighters, they could not breakthrough. Meanwhile, the Irishmen could not break out. They were running out of water and ammunition. With no help forthcoming, they were forced to surrender.
Luckily, the mercenaries didn't slaughter the Irishmen, despite the brutality of the fighting. They were taken prisoner and held captive to extort the United Nations for favorable cease-fire terms. They were released after a month and returned to their Elisabethville base and eventually sent home. The Irish surrender was considered a black eye to the Irish Defence Forces, despite Commandant Pat Quinlan's brilliant defensive perimeter tactics, which are now taught in military textbooks worldwide. Quinlan also ensured each of his men survived and came home.