Rep. Eric Swalwell, D-Calif., serves on the House Intelligence and Judiciary Committees and co-chairs the House Democratic Steering and Policy Committee. Follow him on Twitter at @RepSwalwell . The views expressed in this commentary are his own. View more opinion at CNN.

(CNN) The US airstrike that killed Iranian Maj. Gen. Qasem Soleimani in Baghdad lacked two key elements that any American military strategy must have: the trust of the American people and allies to back us up.

This world is full of bad actors, and how we choose to deal with them has far-reaching implications for our immediate national security and our long-term interests. Our adversaries, including Russia, China and North Korea, work against our interests every day, but we don't call in airstrikes against their top leaders or generals.

Soleimani was among the worst, but he was not from some stateless terrorist organization -- he was a sovereign nation's senior military leader. This is the first time in recent history the United States has eliminated such a figure.

Yet President Donald Trump took this momentous step alone and without any identifiable plan for the ramifications. He did not consult our allies or notify Congress. Had he done so, he would have heard words of caution from prominent officials and allies.

United Nations Secretary-General Antonio Guterres said the world can't afford another war in the region, and leaders "must exercise maximum restraint." Federica Mogherini, the European high representative for foreign and security policy, tweeted that Soleimani's killing was "an extremely dangerous escalation." Even our British allies are urging de-escalation.

Perhaps most importantly, the President took this grave step without the confidence and faith of the American people, three quarters of whom, according to a poll conducted before the killing of Soleimani, do not want to wage war in Iran, and the majority of whom disapprove of Trump's foreign policy. It is not at all clear that his actions are based on credible intelligence, or even that they were undertaken in the best interests of our national security. We are beset by doubt, and rightfully so.

An American president should be knowledgeable, thoughtful and trustworthy enough to discharge his or her duties as commander in chief without immediately being second-guessed. Sadly, that is not how President Trump governs

President Trump's past actions have alienated and angered our allies. And he has forfeited the benefit of the doubt by barraging us with lies on matters involving Russia, by throwing our own intelligence community and public servants under the bus when they contradict him and by ignoring our military experts' advice whenever it fails to fit into his personal political goals.

We've seen this particularly in his conduct regarding Ukraine, for which he was impeached.

During a House Intelligence Committee hearing in November, Marie Yovanovitch, a longtime public servant and the former US ambassador to Ukraine, testified that "the US is the most powerful country in the history of the world in large part because of our values, and our values have made possible the network of alliances and partnerships that buttresses our own strength."

It is a principle that, according to overwhelming evidence, President Trump ignored. He withheld millions of taxpayer dollars from Ukraine, while it was at war with our adversary, to score cheap political points.

And when brave public servants came forward to question and expose his criminal and unconstitutional actions, the President unleashed his wrath on them, calling our diplomats and military personnel -- who served courageously across multiple administrations -- traitors.

Some have asked why what President Trump did in Ukraine matters; this crisis makes it clear.

As Yovanovitch explained in her November testimony, President Trump's rash conduct "undermines the US, exposes our friends, and widens the playing field for autocrats like President Putin. Our leadership depends on the power of our example and the consistency of our purpose. Both have been opened to question."

In short, when our values are called into question and our alliances soften, America is weaker. That is where we find ourselves now as President Trump puts us closer to the brink of full-scale war.

Where was President Trump when all this occurred? The world saw him hanging out at Mar-a-Lago as it learned of the action he took without consulting Congress, without the support of our allies and with the likelihood of blowback that could affect everyone's security and economy. He behaves now as he always has -- as if he's the CEO of his own little fiefdom, and he need answer to nobody.

Protecting American lives is any president's paramount duty, but we must determine whether sound intelligence justified this strike. We must know he is protecting our security and not his own selfish interests.

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President Trump has refused to acknowledge that the Constitution and the law apply to him; now his hubris tells him he has the power to wage war all by himself. None of this is acceptable. Congress must and will do its constitutional duty by wielding its powers of the purse and of oversight. Given his abysmal track record, we cannot and will not take him at his word.

We cannot let him unravel the credibility and trust that this country has spent its entire history earning from its allies and its own people. The world used to know that we cared about our allies, about the rule of law and about democracy. It must know so again; we must not let the President lead us into an unnecessary war on his personal whim.