The Democratic Republic of Congo beat the Republic of Congo 4-2 in the Africa Cup of Nations quarter-final on Saturday. The Republic of Congo team is mostly young and inexperienced, and drawn from a population one-16th the size of the DRC. It was lucky to qualify, getting through only after Rwanda was disqualified for fielding an ineligible player. On paper at least, the result was to be expected. All the same, the game was the most exciting of the tournament so far, with the DRC coming back from two goals down.

The Republic was colonised by France, the DRC by Belgium. Both states gained their independence in 1960. Both suffered civil war in the 1990s, but the consequences have been much graver and longer-lasting in the DRC. Around six million people have died in the deadliest conflict since 1945. The fundamental causes of the war are unresolved, and fighting continues in the eastern region of Kivu.

Last year, Congo expelled more than 130,000 DRC citizens from Brazzaville (the two nations’ capital cities are on opposite banks of the River Congo). They said the operation was to clean up the streets and curb the rise of criminal gangs. In the camps set up to process the displaced people, UN staff recorded accounts of sexual violence and physical abuse at the hands of the Congo authorities.

Relations between the two countries are tense, but politics was kept off the pitch, even if the DRC approached the match with a swagger that could not entirely mask the fear that they might lose to their neighbours.

AfCON features European-based players and European managers, but it resolutely sticks to its awkward calendar, taking place every other January, unlike most international tournaments, which are fitted in between the seasons of the major European leagues. It always finds a way to overcome crises: when Morocco withdrew as host because of the Ebola epidemic, Equatorial Guinea stepped into the breach. AfCON also unites the African diaspora in a way that no other international football tournament can.

As the game got underway, I thought that watching it with my family might have been a bad idea. In Kinshasa and London, everybody was nervous and excited. The match started conservatively. Congo had never beaten DRC, but on the basis of their performance in the group stage, I worried they were going to break my heart. The scoreless first half was frustrating. My uncles kept themselves busy pointing out where Florent Ibengé, the DRC coach, was going wrong. My blood pressure wasn’t going to survive 90 minutes of this. Meanwhile, DRC were wasting chances, much as they had in their last match.

When DRC went 2-0 down, less than twenty minutes into the second half, the colourful language broke out. Lingala has seven vowels and 29 consonants, and my family put them all to good use criticising the defence. New and inventive ways of swearing were learned by all. My aunt shouted that there were children present. It had no effect. Then came 25 minutes of pure magic. A dramatic and scarcely believable four-goal comeback saw Congo collapse against their stronger neighbours. I gave up tweeting just before the third goal. When Dieumerci Mbokani sealed the win in the 90th minute, the living room erupted. Six different languages were being spoken at once.

Reports began pouring in of people taking to the streets in DRC. Car horns blared in Kinshasa, roads were packed in Goma. DRC were through to the semi-finals for the first time since 1998, and people were in the mood to celebrate. Ibenge's name rang out in the streets of Kinshasa, children ran around waving flags, even people carrying the dead home to prepare for the customary period of mourning got caught up in the celebrations.

The DRC is the only team left in the tournament with an African head coach. A third of the squad play in their home league. They deserve to lift the cup on 8 February.

I spoke to my father on the phone after the match. He told me he had known all along we would win. He is 79 years old, and has lived through two coups and two civil wars. ‘The Congolese are a resilient people,' he said. 'Look at our history. Look all we have been through. We are never beaten. We will never be beaten. We will always go forward.’