Thirteen French soldiers were killed when two helicopters collided during an operation against militants in Mali yesterday.<br />'' <br />'' BBC reports that the accident is one of the worst losses of life for the French military in decades. An investigation has begun.<br />'' <br />'' In 2013, France deployed thousands of troops to Mali after militants seized huge parts of the north.<br />'' <br />'' Mali's army has since recaptured the territory but insecurity there continues and the violence has spread to other countries in the region.<br />'' <br />'' France now has 4,500 troops deployed to support the forces of Mali, Mauritania, Niger, Burkina Faso and Chad against the militants.<br />''