Britain has sent 300 soldiers to join the UN peacekeeping mission in Mali, where ISIS and Al Qaeda remain a potent threat.
The troops "will provide a highly specialised reconnaissance capability" and conduct intelligence-gathering patrols while engaging with local communities.
The UN's 14,000-strong mission to Mali, known by its acronym Minusma, is the world's deadliest peacekeeping operation, with 227 fatalities since its launch in 2013 when France intervened to push back militants who seized the north of the country.
"As a permanent member of the UN Security Council, this deployment is a demonstration of our firm commitment to peacekeeping and the importance we place on improving security in the Sahel by protecting local communities," said Britain's Defence Minister, Ben Wallace.
The ministry said the Sahel is one of Africa's poorest and most fragile regions.
"It is marked by chronic poverty, instability, high levels of gender inequality and is highly vulnerable to the effects of climate change," it said.
"Terrorist violence and conflict is sharply on the rise. It is in all our interests that we work together to protect civilians and help build a safer, healthier and more prosperous future for the region."
Most of the soldiers will be based in Gao in northern Mali.
The British contribution was first announced in July 2019.
"We’ve trained hard for the last year to make sure that we are ready for this challenging mission," said the commanding officer of the Light Dragoons, Lt Col Tom Robinson.
"We’re proud to be the first British soldiers to join in this team effort to help combat instability in the Sahel."