The French just gave us another lesson in how not to fight terrorism

The failure of the French military mission, which included up to 5,000 soldiers in what became known as Operation Barkane, demonstrates the perplexing difficulties of waging a counterinsurgency campaign against regional remnants of al-Qaeda and Islamic State. It also raises concerns that Russia and China might step into the geopolitical void left by frustrated and impatient Western governments.

As the United States ponders the lessons of its 20-year struggle against the Taliban in Afghanistan, which ended in a chaotic exit one year ago, France is reconsidering its own strategy in coping with the proliferation of Islamist militants in many of its former African colonies.

President Emmanuel Macron has assigned his leading defense chiefs and advisers to review all of France’s military postures on the continent after the failure to eradicate the threat posed by violent Islamist radicals.

The French departure has opened the door to Russian mercenaries from the Wagner Group, a private security business linked to the Kremlin. Mali’s rulers say France’s decision to break relations left them no choice but to seek other partners. Up to 1,000 Russian mercenaries are estimated to have descended on Mali in recent months, hoping to be paid with gold extracted from local mines. China is also eyeing ways to expand involvement in the region and tap into its mineral wealth.

The Sahel, a vast semiarid region separating the Sahara desert in the north from tropical savannas in the south, has emerged in recent years as a fertile breeding ground for Islamist terrorists who have exploited local grievances against the corruption and brutality of military rulers. The Sahel houses the world’s fastest-growing population and is also one of the poorest, with 80 percent of people living on less than $2 a day. The region encompasses four countries bordering Lake Chad — Cameroon, Chad, Niger and Nigeria — as well as Burkina Faso, Gambia, Guinea, Mali, Mauritania and Senegal.

Around 4 million people have been displaced by the fighting, and many thousands have died. The desperation of the local people has been compounded by persistent drought as climate change spreads desertification through the region. An estimated 50 million people gain their daily sustenance from Lake Chad, which experts predict will evaporate within a decade and force those residents to move, creating still greater hardship for the region.

The French mission in Mali began nine years ago with a promising string of successes in pushing back the advance of Islamist militants toward the capital of Bamako. But relations eventually broke down between French forces and Mali’s military rulers, who seized power two years ago. A second coup took place last year. The army rulers have refused to hand power over to civilians as France had demanded.

The French withdrawal from Mali might jeopardize the fate of the United Nations peacekeeping mission known as MINUSMA, which has some 14,000 troops stationed there. Contingents from Britain and Germany are soon expected to follow the French lead in departing the country.

French forces scored some victories during their long campaign and estimate they have killed about 2,700 militants, yet the Islamist threat continues to grow and attract recruits from disgruntled youths. Islamist guerrillas have expanded beyond Mali into Burkina Faso and Niger and lately have spread terror farther south into coastal states such as Benin and the Ivory Coast.

Regardless of their political or religious fervor, the militants have been able to achieve their territorial gains largely by capitalizing on the pernicious forces of climate change, drought, diminishing food production and, most of all, rapidly surging birthrates.

It is hard to see how these impoverished societies will be able to cope with the quadrupling of their populations in the decades to come, as projected by the United Nations. By the end of this century, Mali is expected to grow from 20 million to 85 million people, and the even poorer state of Niger will rise from 25 million to 165 million people.

As the United States discovered in Afghanistan, even the most modern armies cannot succeed in battling Islamist insurgents with powerful weapons alone. As France is learning the hard way in Africa, the fight against violent Islamists can only be won by combining military prowess with more effective local governance. Curbing corruption and improving the lives of civilians through better schools, medical clinics, clean water and sufficient food supplies are vital.

Defeating Islamist extremists can only be achieved by providing local populations with hope for a better life, not a cause for which to die.