Jalaluddin Haqqani left a horrible legacy before he gave up active leadership of the Pakistan-based network of Islamist extremists he founded.

Haqqani believed Muslims across the world had a duty to “offer themselves” to the cause of fighting the Russians in Afghanistan. And many answered his call.

Was Haqqani's call the real seed of today's global Islamist insurgency? Fountainhead of Jihad, a new book by Vahid Brown and Don Rassler, lays out a fascinating history that supports that view.

The Haqqani network is not just another menacing web of terrorist and criminal enterprises. For decades, it has been an entrepreneur of evil. It practically invented the practice of recruiting “foreign fighters.”

The Haqqanis always saw enlisting and training fighters from other countries as more than a tool for turning back the Soviet invasion of Afghanistan. They expected their battle-hardened brothers would martyr themselves or return home; either way, it would inspire others to carry the cause of Islamist extremism on an ever-widening front.

After the Soviets withdrew from Afghanistan, the Haqqanis helped set up training camps for the next generation of foreign fighters. Indeed, they helped Osama bin Laden set up shop in Afghanistan.

When the Taliban tangled with bin Laden and considered throwing him out of Afghanistan, it was the Haqqanis who stepped in and brokered a truce.

After NATO forces ousted the Taliban and al Qaeda from Afghanistan, the Haqqanis supported the counteroffensive to reestablish the Muslim extremists in the country. One of their most spectacular counterstrikes was the 2009 suicide bombing at Camp Chapman (recreated in the film “Zero Dark Thirty”). The attack killed seven CIA officers. According to former CIA operative Michael Scheuer, “There is no way this operation would have occurred in Khost without the knowledge and active support of Jalaluddin Haqqani and/or his son.”

Today the nightmare network is thriving, protected in part by sympathizers in the ISI, the Pakistani intelligence service. And though it knows full well that the Haqqanis are, in many ways, the root of all evil and cause of many American deaths in Afghanistan, the Obama administration has been reluctant to take on the organization. Indeed, the White House has carefully crafted its definition of who it is fighting to exclude the Haqqani network.

Ignoring the Haqqanis makes it easier for Obama to justify drawing down troops and withdrawing from South Asia. He can simply define victory in a manner that does not actually require him to safeguard U.S. interests in the region or diminish future threats to our nation.

But America will likely pay a price for walking away with the nightmare network intact. “Many jihadis in the region,” Brown and Rassler write, “will be emboldened by the U.S. drawdown and eventual departure from Afghanistan, viewing the event as a victory in their quest to reclaim Muslim lands and rid those areas of Western influence.”

Now, the Haqqani network will get to define for itself the role it will play in the region’s future. If it follows true to form, it will no doubt continue to work against America’s interests in Afghanistan and Pakistan. It will also likely keep its ties and support for the global Islamist insurgency that now actively operates from South Asia to North Africa.

The nightmare network’s best days may well be ahead of it. That is bad news for the United States, and the White House has only itself to blame.

After five years as commander-in-chief over the U.S. forces in Afghanistan, President Obama has done too little to mitigate this threat. In 2014, U.S. combat operations will end with the devil still in the den.

JAMES JAY CARAFANO, a Washington Examiner columnist, is vice president for defense and foreign policy studies at the Heritage Foundation.