The War in Iraq. The War on Terror. These types of "asymmetrical" warfare are the conflicts of the 21st century - and show how difficult it is for the world's only remaining superpower to battle insurgents and terrorists who will fight unconventionally in the face of superior military power.

This change in military conflict may seem sudden. But in his new book, The Sling and the Stone: On War in the 21st Century, Thomas X. Hammes, United States Marine Corps, details how "Fourth Generation Warfare" or "4GW" has evolved over decades, with powerful military forces from economically advanced nations being defeated by seemingly weaker opponents.

Hammes, a full colonel on active duty, spent years training insurgents in various locations around the world. He was stationed in Somalia in the early 1990s before the withdrawal of American troops after the events in Mogadishu. In The Sling and the Stone, he uses this extensive experience and his lifelong study of military history to illuminate how war is evolution, not revolution, and that a "weaker" opponent will continually evolve to use ways to avoid direct military engagement. Instead of winning militarily, an insurgency will work to test the political will of a more powerful nation to stay the course during a war. "We win the battles," he states, "but we lose the war."

Hammes has seen the capability of insurgents firsthand. "I was particularly impressed with two aspects of the men I met," he writes. "First was their utter determination to continue the struggle despite the odds. They were not deterred by fear of death...The second outstanding trait was the remarkable ingenuity they displayed for overcoming problems. I found insurgents are not impressed with conventional power. Any nation that assumes it is inherently superior to another is setting itself up for disaster."

The U.S. has not properly prepared, Hammes contends, for the military needs and political will that will be required to win a "low tech conflict" that is outside the expectations of the Department of Defense's 20th century planning for a short-term conflict with a high-tech, symmetrical enemy like the Soviet Union. Featuring an overview of the first three generations of modern war, Hammes focuses on examples of the evolution of 4GW, and how it will require decades instead of months or years to win. He also examines in detail "transnational" enemies like Al Qaeda, and how the U.S. focus on high-tech weapons designed to overpower an enemy in a short amount of time means little when the enemy has a different concept of the time the conflict will last.

The Sling and the Stone is must reading for anyone who wants to know what it will take for the West to "win" the war on terror. The signs for how it will be fought (and either won or lost) have been developing for decades, and the world's remaining superpower needs to heed the many examples from the recent past in order to secure a lasting victory in the future. As a leading expert on insurgency, asymmetrical warfare, and the unconventional methods used by insurgents like those in Iraq and Afghanistan today, Hammes explains in full detail what to expect from the enemy in the first major war of the 21st century.