They guard mines, train the bodyguards of African presidents and provide security support to UN operations. And increasingly, behind every foreign soldier in the Sahel today, you will find a private military contractor.

Unable to set up permanent bases in Africa, the US army's African command, Africom, is headquartered in Germany and is now reliant on private companies for a range of services - intelligence, transport, logistics, medical evacuation, and sometimes more combat-focused missions.

The 4 October 2017 ambush of an American special forces group in Niger hints at how close those relationships are. Nine soldiers, including four American Green Berets, were killed in the attack by more than 100 fighters aligned to the Islamic State (IS) group.

A Pentagon investigation report into the attack says eight American special forces operators, two other American soldiers and a "intelligence contractor", whose identity and nationality were not revealed, were present.

Drone images showed wounded soldiers being rescued by a Bell 214 civilian helicopter, which belongs to the private company Erickson.

Another private military transport company, Berry Aviation, was put on alert according to researcher and author Joseph Trevithick.

On its website, Berry Aviation makes no secret of its commitment in Africa alongside the US army for freight and passenger transport, parachuting and combat medical evacuations.

In short, it was enough for one mission to go wrong to reveal the names of three private military companies.

A plane used by Berry Aviation in Africa (supplied) For Africom alone, 21 American firms advertise themselves as military service providers in North Africa and the Sahel.

But US firms are not the only one present - dozens of other companies, including from France, the UK, Russia and Ukraine, operate in the area. Their missions range from cooking to armed intervention.

Russia moves into Africa

The Russian private military company, Wagner Group, is gaining a foothold in Africa.

On 24 March, the company took possession of former president Jean-Bedel Bokassa's house in the Central African Republic and transformed it into a centre to train thousands of soldiers for the reconstituted national army.

The appearance of Russian instructors had been preceded in 2017 by arms deliveries from Moscow, which caused upheavals at the UN. France and the US said Russia was violating an international arms embargo applied after the 2013 violence responsible for hundreds of deaths in Central Africa. The UN however signed off on the shipments.

Behind the scenes, it is also reported that Wagner mercenaries were assigned to the close protection of the president, Faustin-Archange Touadéra, while another group was in charge of the security of the country's main diamond mine.

The Russian contractor Wagner Group protects gold, diamond and uranium mines on behalf of Sudan's president, Omar al-Bashir (AFP) Wagner's men are reported to already be operating in Sudan, protecting gold, diamond and uranium mines on behalf of President Omar al-Bashir.

According to Igor Strelkov, a Russian army veteran currently sanctioned by the EU for his leading role in the armed conflict in eastern Ukraine, Wagner was "preparing a mission to South Sudan, and now a search for Soviet-era specialists and translators has begun".

From Libya to Ivory Coast

Other Russian military companies operate in Libya. According to the Russian blog BMPD, the Russian military company RSB sent a demining team to the Benghazi area. Russian private agents also trained soldiers of the Libyan general Khalifa Haftar at the Egyptian base of Sidi Barrani near the Libyan border, according to the Russian blog.

Ukrainian companies also operate in the Sahel. In Mali, Ukrainian helicopters provided airborne medical evacuation support to the UN mission to Mali, UNMISMA, for two years. They are also active in Sudan, Congo and Ivory Coast.

The private military company Omega Consulting Group opened a subsidiary in Burkina Faso and sent several men to the country. Recently, the company recruited French-speaking "operators" with solid combat experience.

Andrei Kekbalo, the head of the company, said in an interview with BBC Ukraine that the salaries offered by his company ranged from $2,000 to $5,000 a month, depending on the danger of the missions.

For positions in Burkina Faso, Omega Consulting Group requires experienced profiles. Experience in Iraq, Yugoslavia, Afghanistan, Africa is rewarded with $14,000 a month.

Today, guerrilla warfare in the Sahel region has become a real business for many actors who sometimes act in total obscurity and on the margins of international legality.

North African countries worry increasingly about this trend while they watching the security situation completely escape their control.

This is an edited translation of the original French.