If you have time read "No Mean Soldier" by Peter McAleese. It's an interesting autobiography where he progresses from the British Paras and SAS in the 1960 to being a mercenary in the 1970 onwards, including working in Angola, South Africa and Colombia up to the early 1990s (I think).
https://www.amazon.co.uk/No-Mean-Sol.../dp/1857972503