The Angolan Civil War (1975-2002)
A building with bullet holes that show how bad things got in Angola. (Creative Commons photo. Attribution to author and info can be found here)
Once Angola was free from Portuguese rule, they immediately started fighting over how to run their new government. This battle became a HUGE proxy war, where the country itself is fighting, but they are receiving a ton of support from more important powers in the hopes of tipping the war to their advantage. The US and USSR both spent tons of money in Angola to try to help groups that supported their ideology and this turned the war into a bloody battle where ½ a million people died.
Fighting in this battle was among the bloodiest in the world at this time. Women and children were allowed to flee the violence, and often fled to neighboring countries, but all men over the age of 10 were viewed as enemies and killed. Thousands of rebels would invade Shaba, Zaire when it came out that their government was involved in helping the government in this war. The hope of this invasion was to spark a civil war in Zaire, but this war never materialized. In reality, the international community (including the US) helped support Zaire so much that they were able to repel these invasions pretty easily. So many Cuban rebels were brought in to help the movement that it made other countries jump into the fight also. South Africa sent in troops sparked the Battle of Cuito Cuanavale (1987-1988) where the Cuban rebels beat the South African military in the biggest battle of African soil since WWII. This law effectively spelled the end of South Africa as a serious
military power in the world. South Africa would agree to let Namibia be independent in the peace talks at the end of this battle, as oversight for the new country was given to the UN.
The violence of this war would displace over 4 million people, which was 1/3rd of the population of the country, and the country never quite recovered from the economic issues this caused. Angola would quickly sink to the bottom of all economic lists of the time period because of its problems. The rebel group in the country that had been supported by the US turned into a terrible group in the coming years, using tons of child soldiers and forcing girls to either marry the rebels or forced to be sex slaves for their men.