France will begin withdrawing its troops from coup-hit Niger this week, a decision that will leave a gaping hole in Western efforts to counter a decade-long Islamist insurgency in the region.

The decision to pull 1,500 troops from Niger was announced last month by President Emmanuel Macron, who said he refused to be “held hostage” by the putschists and was ending military cooperation with the West African country.

The withdrawal is a major blow to French influence in the Sahel and could allow Russia to expand its sway over the region’s vast, insecure scrublands.

Niger was the West’s last key ally in the central Sahel region south of the Sahara Desert until a July 26 coup brought in a military junta which called for France to leave.

Macron also pulled his ambassador out of Niger after the coup.

In a statement on Thursday, the French Armed Forces Ministry said the troops would return to France and that the military exit should be complete by the end of the year.