FORT BENNING, Ga. — “A GREAT deal of intelligence can be invested in ignorance when the need for illusion is deep,” the novelist Saul Bellow once wrote. We should keep that in mind when we consider the lessons from the wars in Iraq and Afghanistan — lessons of supreme importance as we plan the military of the future.

Our record of learning from previous experience is poor; one reason is that we apply history simplistically, or ignore it altogether, as a result of wishful thinking that makes the future appear easier and fundamentally different from the past.

We engaged in such thinking in the years before the attacks of Sept. 11, 2001; many accepted the conceit that lightning victories could be achieved by small numbers of technologically sophisticated American forces capable of launching precision strikes against enemy targets from safe distances.

These defense theories, associated with the belief that new technology had ushered in a whole new era of war, were then applied to the wars in Afghanistan and Iraq; in both, they clouded our understanding of the conflicts and delayed the development of effective strategies.

Today, budget pressures and the desire to avoid new conflicts have resurrected arguments that emerging technologies — or geopolitical shifts — have ushered in a new era of warfare. Some defense theorists dismiss the difficulties we ran into in Afghanistan and Iraq as aberrations. But they were not aberrations. The best way to guard against a new version of wishful thinking is to understand three age-old truths about war and how our experiences in Afghanistan and Iraq validated their importance.

First, war is political. As the 19th-century Prussian philosopher of war Carl von Clausewitz said, “war should never be thought of as something autonomous, but always as an instrument of policy.”

In the years leading up to the wars in Afghanistan and Iraq, thinking about defense was driven by ideas that regarded successful military operations as ends in themselves, rather than just one instrument of power that must be coordinated with others to achieve, and sustain, political goals. Believers in the theory known as the “Revolution in Military Affairs” misinterpreted the American-led coalition’s lopsided victory in the 1991 gulf war and predicted that further advances in military technology would deliver dominance over any opponent. Potential adversaries, they suggested, would not dare to threaten vital American interests.

The theory was hubristic. Yet it became orthodoxy […]

Second, war is human. People fight today for the same fundamental reasons the Greek historian Thucydides identified nearly 2,500 years ago: fear, honor and interest. But in the years preceding our last two wars, thinking about defense undervalued the human as well as the political aspects of war. […]

The hard-learned lesson: Defense concepts must consider social, economic and historical factors that constitute the human dimension of war.

THIRD, war is uncertain, precisely because it is political and human. The dominant assumption of the “Revolution in Military Affairs” was that information would be the key to victory. Concepts of “network-centric warfare,” “rapid, decisive operations,” “shock and awe” and “full-spectrum dominance” suggested that near-perfect intelligence would enable precise military operations and point a straight line to success. But in Afghanistan and Iraq, planning did not account for adaptations and initiatives by the enemy. American forces, deployed initially in insufficient numbers to keep pace with the evolution of those conflicts, struggled to maintain security. The lesson: The wars in Iraq and Afghanistan, like all wars, were contests of will that unleashed dynamics that made future events impossible to predict.

Fortunately, in Afghanistan and Iraq, American forces adapted. For example, in 2005, in western Nineveh Province, our enemies had pitted sectarian communities against one another in a bloody civil war. In the city of Tal Afar, our cavalry regiment first sought to understand the complex environment while building trust with local Iraqi security forces and a beleaguered population. Alongside United States Special Forces and Iraqi soldiers, our troops sought not only to fight the enemy, but also to build security for civilians and promote conflict resolution among competing groups. As Tal Afar’s mayor, Najim Abdullah Abid al-Jibouri, recalled, “Our city was the main base of operations for Abu Musab al-Zarqawi …Our people were barricaded in their homes out of fear; death awaited them around every corner.” But when the Americans came, he added, “With the skill and precision of surgeons they dealt with the terrorist cancers in the city without causing unnecessary damage.”

What we learned: American forces must cope with the political and human dynamics of war in complex, uncertain environments. Wars like those in Afghanistan and Iraq cannot be waged remotely.

Budget pressures and persistent fascination with technology have led some to declare an end to war as we know it. While emerging technologies are essential for military effectiveness, concepts that rely only on those technologies,[…]

Although the defense budget is under pressure, clear thinking about war costs nothing. What we can afford least is to define the problem of future war as we would like it to be, and by doing so introduce into our defense vulnerabilities based on self-delusion.