Overconfidence is how wars are lost − lessons from Vietnam, Afghanistan and Ukraine for the war in Iran were ignored

Wars are rarely lost first on the battlefield. They are lost in leaders’ minds − when leaders misread what they and their adversaries can do, when their confidence substitutes for comprehension, and when the last war is mistaken for the next one.

The Trump administration’s miscalculation of Iran is not an anomaly. It is the latest entry in one of the oldest and most lethal traditions in international politics: the catastrophic gap between what leaders believe going in and what war actually delivers.

I’m a scholar of international security, civil wars and U.S. foreign policy, and author of the book “Dying by the Sword,” which examines why the United States repeatedly reaches for military solutions and why such interventions rarely produce durable peace. The deeper problem with the U.S. war in Iran, as I see it, was overconfidence bred by recent success.

Before the conflict involving Iran, Israel and the U.S. escalated, Energy Secretary Chris Wright dismissed concerns about oil market disruption, noting that prices had barely moved during the 12-day war in June 2025 between Israel and Iran. Other senior officials agreed.

What followed was significant: Iranian-aimed missile and drone barrages against U.S. bases, Arab capitals and Israeli population centers. Then Iran effectively closed the Strait of Hormuz, through which roughly 20% of the world’s oil supply passes daily − not with a naval blockade, not with mines or massed anti-ship missiles, but with cheap drones.

A few strikes in the vicinity of the strait were enough. Insurers and shipping companies decided the transit was unsafe. Tanker traffic dropped to zero, although the occasional ship has made it through recently. Analysts are calling it the biggest energy crisis since the 1970s oil embargo.

Iran’s new supreme leader, Mojtaba Khamenei, has since vowed to keep the strait closed. U.S. Sen. Chris Murphy, a Connecticut Democrat, reported after a closed-door briefing that the administration had no plan for the strait and did not know how to get it safely back open.

With no embassy in Tehran since 1979, the U.S. relies heavily for intelligence on CIA networks of questionable quality and Israeli assets who have their own country’s interests in mind. So the U.S. did not anticipate that Iran had rebuilt and dispersed significant military capacity since June 2025, nor that it would strike neighbors across the region, including Azerbaijan, widening the conflict well beyond the Persian Gulf.

The war has since reached the Indian Ocean, where a U.S. submarine sank an Iranian frigate 2,000 miles from the theater of war, off the coast of Sri Lanka – just days after the ship had participated in Indian navy exercises alongside 74 nations, including the U.S.

The diplomatic damage to Washington’s relationships with India and Sri Lanka, two countries whose cooperation is increasingly important as the United States seeks partners to manage and mitigate Iran’s blockade, was entirely foreseeable. Washington has put them in a difficult position, with India choosing diplomacy with Iran to secure passage for its vessels and Sri Lanka opting to retain its neutrality, underscoring its vulnerable position.

But U.S. planners didn’t foresee any of this.

The swift military intervention by the U.S. in Venezuela in January 2026 produced rapid results with minimal blowback − appearing to validate the administration’s faith in coercive action.

But clean victories are dangerous teachers.

They inflate what I call in my teaching the “hubris/humility index” − the more a leadership overestimates its own abilities, underestimates the adversary’s and dismisses uncertainty, the higher the score and the more likely disaster will ensue. Clean victories inflate the index precisely when skepticism is most needed, because they suggest the next adversary will be as manageable as the last.

Political scientist Robert Jervis demonstrated decades ago that misperceptions in international relations are not random but follow patterns. Leaders tend to project their own cost-benefit logic onto opponents who do not share it. They also fall into “availability bias,” allowing the most recent operation to stand in for the next.

The higher the hubris/humility index, the less likely there is to be the kind of strategic empathy that might ask: How does Tehran see this? What does a regime that believes its survival is at stake actually do? History shows that such a regime escalates, improvises and takes risks that appear irrational from an outside perspective but are entirely rational from within.

Recent cases reveal this unmistakable pattern.

American war planners believed material superiority would force the communists in Hanoi to surrender.

It didn’t.

American firepower alone didn’t lead to military defeat, much less political control. The Tet Offensive in 1968 – when North Vietnamese and Viet Cong forces launched coordinated attacks across South Vietnam – shattered the official U.S. narrative that the war was nearly won and that there was “light at the end of the tunnel.”

Athough the U.S. and South Vietnamese forces ultimately repelled the attacks, their scale and surprise caused the public not to trust official statements, accelerating the erosion of public trust and decisively turning American opinion against the war.

The U.S. loss in Vietnam didn’t occur on a single battlefield, but through strategic and political unraveling. Despite overwhelming superiority, Washington was incapable of building a stable, legitimate South Vietnamese government or recognizing the grit and resilience of the North Vietnamese forces. Eventually, with mounting casualties and large-scale protests at home, U.S. forces withdrew, ceding control of Saigon to North Vietnamese forces in 1975.

The U.S. failure was conceptual and cultural, not informational. American analysts simply couldn’t picture the war from their opponent’s perspective.

The Soviet Union in Afghanistan in 1979 and the United States in Afghanistan after 2001 conducted two different wars but held the same deadly assumption: that external military force can quickly impose political order in a fractured society strongly resistant to foreign control.

In both cases, great powers believed their abilities would outweigh local complexities. In both cases, the war evolved faster − and lasted far longer − than their strategies could adapt.

This is the case that should most haunt Washington.

Ukraine demonstrated that a materially weaker defender can impose huge costs on a stronger attacker through battlefield innovation: cheap drones, decentralized adaptation, real-time intelligence, and the creative use of terrain and chokepoints to find asymmetrical advantages. The U.S. watched it all unfold in real time for four years and helped pay for it.

Iran was also watching − and the Strait of Hormuz is the proof.

Iran didn’t need a navy to close the world’s most important energy chokepoint. It needed drones, the same cheap, asymmetric technology Ukraine has used to blunt Russia’s onslaught, deployed not on a land front but against the insurance calculus of the global shipping industry.

Washington, which had underwritten much of that playbook in Ukraine, apparently never asked the obvious question: What happens when the other side has been taking notes? That is not a failure of U.S. intelligence. It is a failure of strategic imagination − exactly what the hubris/humility index is designed to highlight.

Iran does not need to defeat the U.S. conventionally. It needs only to raise costs, exploit chokepoints and wait for a fracture among U.S. allies and domestic political opposition to force a fake U.S. declaration of victory or a genuine U.S. withdrawal.

Notably, Iran has kept the strait selectively open to Turkish, Indian and Saudi vessels, rewarding neutral countries and punishing U.S. allies, driving wedges through the coalition.

Historian Geoffrey Blainey famously argued that wars start when both sides hold incompatible beliefs about power and only end when reality forces those beliefs to align.

That alignment is now happening, at great cost, in the Persian Gulf and beyond. The Trump administration scored high on the hubris index at exactly the moment when it most needed humility.

This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Monica Duffy Toft, Tufts University

Monica Duffy Toft does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.