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Less apparent is how he has recently expanded his shadow role in matters of the military and intelligence, an extension of his experiences as a young Army tank unit captain in Germany and his first administration job as C.I.A. director.

With command of the Pentagon in flux since Jim Mattis resigned in December, Mr. Pompeo has asserted his views much more forcefully in national security debates, current and former officials say.

He is also widening his network in the cabinet. Gina Haspel, the C.I.A. director, was Mr. Pompeo’s deputy at the agency and is keen to maintain strong relations with him, knowing that that helps keep her in Mr. Trump’s good graces, the officials say. And the incoming acting defense secretary, Mark T. Esper, was a classmate of Mr. Pompeo at West Point. His presence could help bolster Mr. Pompeo’s influence — especially in counterpoint to Mr. Pompeo’s main power rival but frequent policy ally, John R. Bolton, the aggressive national security adviser.

On Iran, Mr. Pompeo has been the public face of the administration’s hawks, and internally he has even argued for policies that generals have deemed too provocative.

“What Pompeo and Bolton have done is drive the president into a corner,” said Wendy R. Sherman, a former top State Department official who helped lead negotiations with Iran in the Obama administration. “The maximum pressure campaign through the sanctions has only strengthened the hard hard-liners in Iran, just like Pompeo and Bolton are the hard hard-liners in our country.”

Prone to bluster and flashes of anger, Mr. Pompeo regularly uses military jargon when speaking of diplomacy — “mission set,” “commander’s intent,” diplomats as “warriors.” He has even described his wife, Susan Pompeo, a frequent traveling companion, as a “force multiplier.”

Still, Mr. Trump voices support for the “maximum pressure” campaign of economic sanctions on Iran that Mr. Pompeo and Mr. Bolton have pushed. On Friday, Mr. Trump said on Twitter: “Sanctions are biting & more added last night. Iran can NEVER have Nuclear Weapons, not against the USA, and not against the WORLD!”

No officials could point to any new sanctions, though the president said on Saturday that he planned to impose “major” additional sanctions on Monday. And Mr. Trump has never addressed the common argument that the reimposition of crippling sanctions last year is what has pushed Iran to lash out. Iran had spent a year working with European nations to try to contain the damage from Mr. Trump’s withdrawal from a 2015 nuclear containment deal that major world powers support.

In the Situation Room on Thursday, Mr. Pompeo argued that in addition to launching a strike, the administration should continue the sanctions campaign and let the recent cut in oil revenues sink in, according to an official familiar with the debate.

“Of all the top administration officials, I think Pompeo is the most secure and also the best at channeling Trump,” said Mark Dubowitz, chief executive of the Foundation for Defense of Democracies, who advises Trump administration officials and advocates sanctions on Iran.

But Mr. Pompeo’s militant stand on Iran has led some prominent Trump supporters to push for his ouster because of what they see as a betrayal of Mr. Trump’s “America First” isolationism. On Thursday night, after Mr. Trump called off the strike, Douglas Macgregor, a retired army colonel, told Fox News that Mr. Trump “needs to get rid of the warmongers. He needs to throw these geniuses that want limited strikes out of the Oval Office.”

Mr. Trump has said he reins in Mr. Bolton, but has never mentioned doing the same with Mr. Pompeo.

If staying in Trump’s good graces is one guiding star for Mr. Pompeo, another is his religion. He has been open about the influence of Christian theology on his policies, especially those involving the Middle East.

A telling moment came in March when Mr. Pompeo visited Jerusalem, where he spoke with Prime Minister Benjamin Netanyahu about the threat that Iran poses to Israel. An interviewer from the Christian Broadcasting Network posed a question around a biblical tale about a queen who saved Jews from being massacred by a Persian viceroy: Did Mr. Pompeo think President Trump had been “raised for such a time as this, just like Queen Esther, to help save the Jewish people from the Iranian menace?”

“As a Christian, I certainly believe that’s possible,” Mr. Pompeo said, noting with pride “the work that our administration’s done, to make sure that this democracy in the Middle East, that this Jewish state, remains. I am confident that the Lord is at work here.”

One month after starting his job in April 2018, Mr. Pompeo worked with Mr. Trump to withdraw from the Iran nuclear deal. And he went much further: He announced 12 demands that Iran would have to meet before the United States considered lifting renewed sanctions. Mr. Pompeo has a grand goal of undermining what he calls Iran’s “expansionist foreign policy” — a mission that Mr. Trump never mentions. Iranian leaders see meeting the 12 demands as tantamount to regime suicide, analysts say.

“Most of them are unacceptable to the Iranians,” said R. Nicholas Burns, the top career State Department official under President George W. Bush. “As a result, we’ve had zero contact with them and no ability to influence their behavior.”

Mr. Pompeo’s drive to confront Iran on all fronts has become conflated with the aim of keeping limits on its nuclear program. By contrast, top officials under Mr. Bush and Mr. Obama kept a compartmentalized focus on the nuclear issue, since that was more easily addressed alone.

In April, Mr. Pompeo and Mr. Bolton pushed Mr. Trump to designate Iran’s Islamic Revolutionary Guard Corps as a terrorist organization, even though Pentagon and C.I.A. officials opposed the action, saying it could provoke attacks. Mr. Pompeo then announced the end of permission for eight governments, including American allies, to bypass sanctions in buying oil from Iran. Those moves, analysts say, have led to the current crisis.

In recent classified briefings to Congress and in public declarations, Mr. Pompeo has discussed ties between Iran and Al Qaeda. Democratic and some Republican lawmakers say that is a blatant attempt to lay the groundwork for bypassing the need for new congressional war authorization if Mr. Trump decides to strike Iran.

Lawmakers also question Mr. Pompeo’s role in stalled policy on other signature Trump issues, such as Venezuela and North Korea. The North, unlike Iran, actually has a nuclear arsenal.

And lawmakers have grilled Mr. Pompeo on his unwavering support of the crown prince of Saudi Arabia, Mohammed bin Salman, who American intelligence officials say was responsible for the killing of the columnist Jamal Khashoggi and who is leading an air war in Yemen that has resulted in a humanitarian disaster. Legislators are also furious that Mr. Pompeo has sought to circumvent the congressional approval process for arms sales to Saudi Arabia and the United Arab Emirates.

Critics say that growing scrutiny of Mr. Pompeo is warranted given his unrelenting attacks on Secretary of State Hillary Clinton during the Benghazi hearings when he was a congressman — and given the potential threats to the United States resulting from the administration’s foreign policy.

“I think Pompeo,” Ms. Sherman said, “is very much an architect of where we are now.”