I’m a former Pentagon adviser. Trump has utterly failed to understand how wars work

Donald Trump began his second term with a vision of peace. “We will measure our success not only by the battles we win,” he said during his inauguration, “but also by the wars we end, and perhaps most importantly, the wars we never get into.” Just over 19 months later, with the US mired in a conflict with Iran that has tested American credibility and deterrence, Trump’s words stand as a striking contrast to the reality he has created in the region, a reality brought on by a grave miscalculation that US military might could address what are fundamentally political issues. Only this week, the US and Iran engaged in yet another cycle of tit-for-tat attacks. President Trump is considering a plan for periodic strikes on Iran’s radar, air defence and anti-ship missile sites in and around the Strait of Hormuz, aiming to stop Tehran rebuilding its capacity to attack ships, according to one report. Iranian attacks on US bases at the weekend could push Trump to greenlight the plan, the report said, citing officials. Trump’s renewed taste for military action against Iran – six months into his war – is particularly striking coming so soon after his Treasury Secretary, Scott Bessent, announced an “economic D-Day” of increased sanctions aimed at squeezing the country into submission and ending the war. That announcement was meant to prevent exactly this kind of return to military means. Trump was never a dove, nor did he claim to be. His first presidency demonstrated a clear willingness to use military force, albeit with a proclivity for short-term targeted operations with a clear objective and defined timeline. In April 2017 and again a year later, Trump ordered strikes against Syrian chemical weapons sites and an airbase where the US believed “regime aircraft took off for a deadly chemical attack against civilians”. In January 2020, he ordered a drone strike that killed the Iranian Quds Force commander Qassem Soleimani. These operations did not paint a picture of a trigger-happy president eager to rush to war, but rather of one who preferred spectacular, time-bound uses of force that appeared capable of producing an immediate tactical result, if not necessarily translating to long-term strategic success. His penchant for such strikes continued when he assumed the presidency for the second time. Empowered by what he perceived as successful operations in Venezuela earlier this year, and during the US-Israeli “12-day war” on Iran in June 2025, he embarked on a course previous US presidents had sought to avoid and one that several Gulf allies had warned him against: an all-out war with Iran. Encouraged by a sustained pressure campaign from the Israeli Prime Minister, Benjamin Netanyahu, and his allies in Washington, primarily hawkish Republicans who saw this escalation as necessary and overdue, Trump appeared convinced that this, too, would be a quick and decisive show of strength. Only this time, he gravely miscalculated. A banner at Tehran’s Azadi Square. The President has gravely miscalculated the current conflict (Photo: Fatemeh Bahrami/Getty) My tenure as an adviser in the Office of the Secretary of Defence for the Middle East coincided with significant events in the region: the US drawdown from Iraq in 2009, the Arab Spring, the Nato-led Libya campaign, and the counter-Isis mission, among others. Both in real time and in hindsight, it was clear that the use of military force to achieve political aims too often created the conditions for further conflict down the road. Trump is not the first, nor may he be the last, president to fail to heed several lessons he should have learned from his predecessors. First, that military power is a tool of political strategy, not a substitute for one. Trump attacked Iran with a stated intention at the outset of regime change and calls for the Iranian people to rise up as well as stating Iran could never acquire a nuclear weapon. He then backed away from that objective, offering a set of mixed messages focused primarily on Iran’s ballistic missile programme, its navy, and its support for proxies, before coming full circle, to the nuclear issue and regime collapse through expanded economic sanctions as stated by Bessent – all the while having inadvertently contributed to the creation of an entirely new problem in Iran’s closure of the Strait of Hormuz. These are not interchangeable objectives, nor do they carry the same strategic rationale. Without a clear rationale or objective, ad hoc, reactive use of military force became, for a time, the strategy in itself. Second, to be prepared for unexpected scenarios. In a 2014 interview, Robert Gates, the first of three secretaries of defence I served under and who opposed the intervention in Libya, said the US did not have “enough humility about our inability to predict unforeseen consequences” and specifically recounted that, in the Bush administration, he had been against military action in Iran, stating that “the idea of acting precipitously to go after the Iranians or to enable the Israelis to go after them where we didn’t know the consequences but could well lead to a major regional war I felt was too risky”. In Trump’s case, while we cannot know the scenarios that were presented to him by his team, the President certainly did not make the case to the American public for a months-long war, nor did he consider the warnings of our Gulf allies, who would bear the most immediate consequences of any prolonged conflict. And just as he underestimated the Iranian regime’s resolve to survive, Trump also underestimated its capacity to retaliate. The administration appears to have assumed that Tehran’s options were limited and that any response could be contained. That assumption ignored both Iran’s demonstrated tolerance for absorbing and redirecting pain and its ability to impose costs asymmetrically, whether through proxy attacks in the region, pressure on maritime routes, or threats to civilian and energy infrastructure across the Gulf. Third, that defining victory at the outset is necessary for the application of proportionate military force. Trump started the war with Iran without defining what victory would actually look like, and as such, has failed to align force with objective. If the objective were regime change, that could not have been achieved through an air campaign and naval blockade alone. If it were deterrence, the war has seemingly produced the opposite by convincing Tehran that only a higher cost imposed on the United States and its partners can prevent future attacks, as evident in Iran’s reaction to the latest threats of aggressive economic sanctions and further threats of force by Trump. If the objective were to force Iran back to the negotiating table on American terms, that too seems remote in the near term. States do not tend to negotiate under maximal pressure or humiliation when survival is at stake. Rather, they may attempt to escalate until they can negotiate from a position of restored leverage and respect (the Iranian parliament speaker and negotiator Mohammad Ghalibaf said on 21 August that “we will not allow people to trample on our dignity and honour”), or until a dignified off-ramp is offered to them, as was the case during the run-up to the Obama-era Iran deal. In the end, his zeal for awesome displays of American power, his desire to leave a legacy of “peace through strength” in the Middle East, and his disregard for the lessons of the past led Trump into war without a clear political strategy, defined end state or diplomatic bridge to achieve it. Force may have weakened Iran, but it cannot, by itself, deliver the peace he promised. Shorts