Even if Tehran was responsible for the oil strike, the US has no cause for war. Saudi Arabia, not America, was attacked. The kingdom is not a treaty ally; US military personnel have not signed up as bodyguards for the Saudi royals. Nor is there a good policy reason to underwrite the defence of a regime which actively promotes extremism, shares virtually no Western values, and routinely undermines American interests.

Higher oil prices are not a good reason for war. The costs of any conflict are likely to run far higher, especially considering the blood to be shed. A wealthy nation such as the US can adapt to higher energy bills.

Washington should always treat military action as a last resort, to be used only in the face of compelling circumstances, which are not evident today. In fact, the importance of Middle Eastern oil has steadily declined. The US has become the world’s largest petroleum producer. Other sources have come online to diversify today’s energy market. Losing Saudi supplies has roiled short‐​term oil markets, but that impact will fall over time. Moreover, Washington has done far more to destabilise the energy marketplace by driving down the sale of Iranian and Venezuelan oil and hindering Russian energy production. The US cares far more about low energy prices in theory than in practice.

Finally, a Middle Eastern war, likely characterised by attacks on Iranian and Saudi oil fields, the interdiction of tanker traffic, and a mix of proxy and asymmetric assaults on a variety of targets, would do even more to hike petroleum prices. Of course, everything could work better than expected, but what recent war—consider the experience of Afghanistan, Libya, Yemen, and Iraq—turned out well?

Fear of regional instability is no better argument. Washington favours stability except when it doesn’t, which is often. The invasion of Iraq had a catastrophic impact on the entire region.

The US promoted a series of smaller, but still brutal, complicated, and highly destabilising conflicts: Libya, Syria, and Yemen. The latter has entangled Saudi Arabia in a seemingly endless war which led to increasing retaliatory strikes on its homeland. If the Trump administration really wants to reduce regional turmoil, rather than start another Middle Eastern war, with a larger, more populous, wealthier, and better prepared adversary, Washington should end involvement in and support for ongoing conflicts.

The tired clichés of protecting “credibility” and demonstrating “resolve” have been trotted out, used whenever Washington’s ivory tower generals urge military attacks which would undermine American interests. The worst reason to start a potentially major war is to convince other nations that Washington will go to war. Of course it will: it has done so more often than any other nation since the end of the Cold War.

What more is required to demonstrate the foolish aggressiveness of US officials who consistently overestimate the effectiveness of military action and underestimate the difficulty of international social engineering? Instead of acting as “Saudi Arabia’s bitch”, in the words of Democratic presidential candidate Tulsi Gabbard, the Trump administration should truly put America first.

Having loaded the kingdom with high‐​tech weapons, Washington should insist that Saudi Arabia take responsibility for defending itself. The royal family is quite ruthless in targeting internal critics, kidnapping, imprisoning, murdering, and even dismembering those who dissent. The regime seemingly lacks nothing, certainly not money, weapons, or personnel.

Its problem is more fundamental: legitimacy. Who wants to die to protect a pampered elite which loots the public and lives in luxury, citing its relationship with a long‐​dead tribal leader? At least Iran’s rulers claim to represent the divine. Saudi Arabia’s royals represent a decadent past that long ago should have disappeared.

Let them persuade their people to fight. Trump should also end his economic war on the Iranian people. Lost in the administration’s militaristic bluster is the fact that there were no Iranian threats against oil production and Gulf transit when both Washington and Tehran were observing the Joint Comprehensive Plan of Action.

The president abandoned the agreement and launched a debilitating economic attack on Iran, which international law views as an act of war. Attempting to destroy the Iranian economy and starve the Iranian people was guaranteed to generate a response. If Tehran accordingly is responsible for striking the chief Middle Eastern supporter of America’s economic aggression, the administration has no one to blame but itself. There are consequences for foolish actions, even for Saudi Arabia and the US.

Finally, the president should end American support for Saudi Arabia’s aggressive war against its impoverished neighbour.

Riyadh has spent the last four years brutalising one of the world’s poorest nations, in order to restore to power a pliant ally. Yemen’s insurgent Houthis have responded with increasingly effective drone attacks on Saudi Arabia, sparking shocked whining from Saudi royals who imagined that they could kill without consequence.

After slaughtering thousands of Yemeni civilians—humanitarian groups figure that Riyadh and its allies are responsible for two‐​thirds to three‐​quarters of the casualties and destruction in Yemen—the kingdom has no credibility in complaining about energy and economic losses. If the royals prefer not to be targets, they should end their attacks on Yemen. Indeed, by making the cost of war more evident to the Saudis and America, the oil strike may be the best blow yet struck for peace.

The threat of additional attacks offers a strong incentive for the royals to make peace. During the presidential campaign Trump criticised the Saudis for depending on America for their defence. Once taking office, however, he delegated his policy to Crown Prince Mohammad bin Salman. Yet there is no more irresponsible government in the Middle East: attacked its neighbour Yemen, kidnapped Lebanon’s prime minister, underwrote brutally repressive regimes in Bahrain and Egypt, promoted civil war in Libya, backed anti‐​American Islamist insurgents in Syria, initiated a diplomatic offensive against neighbouring Qatar, promoted intolerant Wahhabist theology around the world, and ignored the funding of terrorist groups including Al Qaeda.

The president should stop exhibiting wilful blindness towards the Saudis. If he cared about America’s future, he would reclaim control of US Middle Eastern policy from Riyadh. And start ending old wars rather than starting new ones.