The defense secretary, Pete Hegseth, prayed during a religious service at the Pentagon that there be “overwhelming violence of action against those who deserve no mercy”.

The Christian worship service, held on Wednesday before military and civilian workers at the Pentagon, was Hegseth’s first since the Iran war began, the Associated Press reported.

Hegseth called for violence during a prayer he said originated from a military chaplain and was given to troops after Nicolás Maduro, the president of Venezuela, was captured by the US, the AP said.

“Let every round find its mark against the enemies of righteousness and our great nation,” Hegseth said in the prayer service. “Give them wisdom in every decision, endurance for the trial ahead, unbreakable unity, and overwhelming violence of action against those who deserve no mercy.”

The remarks came a day after Hegseth announced changes to the military’s chaplain corps, which he said in a video message had been “infected by political correctness and secular humanism” until they were “watered down” to be “nothing more than therapists” who focused more on “self-help and self-care” than faith or virtue.

The chaplain corps would have its religious affiliation codes reduced from about 200 different faith codes down to 31 codes, he said. The chaplains would also no longer wear their officer rank insignia on their uniforms, but instead their religious insignia. The changes were in pursuit of “making the chaplain corps great again”, he said.

Hegseth instituted monthly prayer sessions at the Pentagon during his tenure, though all of the prayer meetings have been presided over by evangelicals, the AP reported.

Hegseth is member of a church affiliated with the Congregation of Reformed Evangelical Churches, founded by Doug Wilson, who self-identifies as a Christian nationalist and has himself led a session of the prayer service at the Pentagon.

Hegseth’s insertion of his Christian faith into his role has drawn criticism and legal complaints. Hegseth’s comments on the Iran war have included religious context – he said in a TV interview that the US is “fighting religious fanatics who seek a nuclear capability in order for some religious Armageddon”.

Military veterans previously told the Guardian that Hegseth’s use of religion in the department was causing division and could weaken the military.

“We’re gonna see a lot of Christian nationalists join the military,” Kristofer Goldsmith, an Iraq war veteran and the CEO of non-profit watchdog Task Force Butler, told the Guardian last year. “They’re not gonna perform very well, and our national security will suffer for a generation for it, because those that don’t wash out will be toxic leaders.”

Americans United for Separation of Church and State filed lawsuits against the defense and labor departments this week to access public records about prayer services at the departments, including how invited speakers, recordings of prayers and any complaints from employees about the services. The records will help the organization understand whether the departments are staying neutral on religion and respecting workers’ religious freedom, the group said.

“The federal government’s role is to serve the public, not to proselytize,” Americans United President and CEO Rachel Laser said in a statement. “Even if these prayer services are presented as voluntary, there is pressure on federal employees to attend in order to appease their bosses – especially since these services occur amidst the Trump administration’s campaign to punish anyone who doesn’t comply with its Christian Nationalist agenda.”