The global war on terror that the United States launched in 2001 was one it could choose to leave. Washington invaded Iraq and years later, it withdrew from Afghanistan. Neither exit was clean — an insurgency returned in one country and the Taliban in the other. Still, America could unilaterally decide its campaigns were over.
That power remains. Washington can stop fighting Iran, raise or lower its support for Ukraine and broker a ceasefire between Hamas and Israel. What has changed is that declaring its involvement over won't keep it out. Even if a war pauses or a deal is reached, the conflict may erupt again, pulling America back in.
Three conflicts, albeit not equivalent, taking place across regions show that the United States can influence their course yet cannot control their endings. In Ukraine, the United Nations has documented tens of thousands of civilian casualties since Moscow's full-scale invasion of Kyiv in 2022. While the United States can alter the scale of its support to Ukraine or push Kyiv toward negotiations, it cannot force Russia to stop fighting or compel either side to accept peace. The decision to end the war rests with the parties fighting it.
In Gaza, Israel's military campaign has triggered roughly 75,000 Palestinian deaths and the US-brokered ceasefire hasn't meant an end to the dying, highlighting a pause in violence is not the same as an end to the conflict. America may help negotiate a ceasefire, it can't guarantee the conflict won't resurface.
A twelve-day war between Iran and Israel-Iran June 2025 ended quickly through negotiation, killing over a thousand people in Iran and 28 in Israel. Eight months later, the United States and Israel launched a far larger military campaign aimed at regime change in Iran. A Pakistan-mediated ceasefire took hold for a brief period before collapsing in July.
A war that seemed to prove endings are negotiable was followed, within months, by one that has resisted every attempt to close it. America, again, hasn't lost the ability to leave the war; the challenge is that leaving doesn't guarantee the conflict is over. Even if a compromise is reached with Tehran, an Iran-Israel conflict may still draw Washington in.
Ukraine, Gaza and now Iran show how easily that control slips away. The cost of a war that cannot be ended is not just money and lives. It is also the military capacity consumed fighting those wars. During the Iran-Israel war last year, the United States reportedly fired 150 THAAD interceptors to protect Israel, more than a quarter of its inventory in addition to 80 Standard Missile-3s to neutralize the incoming Iranian projectiles.
The 2026 escalation drained the reserves further with the Center of Strategic and International Studies estimating the US inventories of THAAD and Patriot interceptors had fallen to fewer than 1,000 and about 250 respectively. This is a different sort of scarcity than a strained budget. Unlike money that can be raised, borrowed or reallocated, these interceptors take years to build on a production line that can't be scaled up overnight. This shortage is affecting Ukraine and other US allies in the Indo-Pacific relying on America to replenish their missile stockpiles.
Global military spending hit a record $2.9 trillion in 2025 — 2.5% percent of world output, the highest share since 2009. Although global outlays grew by 2.9%, expenditures rose by 9.2% outside the US including a 14% spike in Europe and 8.1% in Asia and Oceania. And one reason it keeps climbing is that no government can confidently predict the number of conflicts its arsenal may need to cover.
Insecurity triggers an acceleration in rearmament that outpaces industrial capacity. Given a multi-year timeline is required to expand defense production, a war fought to exhaustion in one theater weakens deterrence in the other. As Ukrainian President Volodymyr Zelensky said his country had about two-and-a-half times fewer interceptors than it did in 2025. This self-reinforcing vulnerability emerges when states draw on the same finite supply chain.
This does not mean that every war should be rushed to a close. A settlement can be worse than war if it only postpones the next round. Ukraine, for example, can't be expected to secure peace by accepting terms that leave it exposed to another invasion. The real challenge is not stopping the war but whether it promises an ending that actually holds.
Twenty-five years after the towers fell, the United States is still capable of fighting wars it could choose to leave. What it is yet to learn is how to survive wars in which leaving is possible but ending, and rearming for the next, is not.
*My article (unedited) first appeared at Eurasia Review