Feb. 20, 2017 7:06 p.m. ET
Defense Secretary Jim Mattis appears to be at odds with President Donald Trump on Russia and other key issues, setting up potential discord but also helping to nudge the White House toward more conventional policy stances.
In recent days, other top administration officials have aired foreign-policy views that don’t align perfectly with the new president. Vice President Mike Pence and Secretary of State Rex Tillerson, for example, have suggested a tougher line with Russians, demanding they de-escalate violence in Ukraine.
But it is Mr. Mattis who has differed with the president on the most issues. And while that could set up a clash with a White House that has said those who don’t agree with the president should leave, the defense chief seems to have had the most success in prodding Mr. Trump away from some of his positions.
While the president has turned to generals for several key posts—on Monday naming Army Lt. Gen. H.R. McMaster as national security adviser—Mr. Mattis remains the highest-profile and most widely respected of all the generals in the administration. Further, on some matters, including Russia and Ukraine, Mr. Mattis has strong allies, including Mr. Pence.
To a degree, Mr. Mattis’s divergence with the White House reflects his lack of political experience. He is a retired Marine four-star general, and military officers, American officials note, don’t always have much experience with the political aspects of their jobs.
But Republicans say there is a degree of consternation with Mr. Mattis in the White House, partly because of his desire to install in key Pentagon posts Democrats or Republicans who were critical of Mr. Trump during the campaign.
Despite the frustration over the appointments, Mr. Trump remains a fan of Mr. Mattis, valuing his counsel, according to a Republican official close to the administration. Mr. Trump has clear admiration for Mr. Mattis’s plain talk, and Mr. Pence mentioned him Monday to make the point there was strong leadership in the administration’s national-security team.
At nearly every stop of his second overseas trip that finished Tuesday, after a visit to Iraq, Mr. Mattis made clear his own positions, which haven’t always squared with the public pronouncements of the president.
The disagreements started in the job interview. Mr. Mattis, widely respected for his no-holds-barred battlefield focus, told Mr. Trump during that meeting in December that he didn’t believe torture worked and that he thought the North Atlantic Treaty Organization was a critical military alliance that shouldn’t be abandoned.
“If we did not have NATO today, we would need to create it,” he said at his January confirmation hearing with a Senate panel.
Mr. Trump, enamored of Mr. Mattis’s reputation and the name the media conferred upon him years ago, Mad Dog Mattis, was impressed. Within days, the president, while saying he still believed torture worked, deferred to his soon-to-be defense secretary, saying he would allow Mr. Mattis to “override” him on the issue.
Mr. Trump subsequently has altered his stance on the value of NATO , but maintained that European allies should pay more for collective defense. Mr. Mattis dutifully carried that message to two stops in Europe last week, in Brussels and at a security conference in Munich.
On other issues, there appears to be more daylight between Mr. Mattis and the president. In Abu Dhabi, asked if the U.S. was interested in seizing Iraqi oil fields, an idea that Mr. Trump had toyed with publicly during the campaign and again at a speech at CIA headquarters the day after his inauguration, Mr. Mattis dismissed the idea .
“We are not in Iraq to seize anybody’s oil,” Mr. Mattis told reporters.
Mr. Mattis has also taken a different stance on Russia than Mr. Trump, although there are signs the administration is moving his way. The defense secretary and Mr. Pence have said Russia must be held accountable for its actions in Ukraine and that Moscow’s annexation of Crimea wouldn’t be recognized. Mr. Tillerson and U.N. Ambassador Nikki Haley have also taken a tough line against relaxing sanctions.
During his visit to Brussels, Mr. Mattis spoke skeptically about military cooperation with Russia, even as he said political leaders—presumably including Mr. Trump—would engage to find “a way forward.”
Mr. Trump, as Mr. Pence noted Monday, continues to believe that more cooperation with Moscow is possible. In his news conference last week , Mr. Trump said the U.S. political climate was poisoning relations with Moscow and “makes it much harder to make a deal with Russia.”
Before he was confirmed, Mr. Mattis was seen as a steady hand who knew the issues and inspired the military. Supporters of his knew he had enough credibility with Mr. Trump that he could act as a buffer, helping to rein in some of the president’s unfiltered ideas while strengthening the fight against Islamic State.
While more junior-level dissenters have been ushered out , there may be more latitude for the top administration officials. Mr. Pence wasn’t afraid during the campaign to contradict Mr. Trump on policy matters, including relations with Russia.
Like Mr. Mattis, Mr. Pence has sought to clarify the administration’s positions in ways that don’t always seem in perfect alignment with the president. While Mr. Trump has been an enthusiastic backer of Britain’s move to leave the European Union, for example, Mr. Pence offered a warm embrace of the EU on Monday.
Mr. Pence has also shown a political deft touch. Asked on Monday what he thought about the media given Mr. Trump’s attacks on the press as an “enemy of the people,” Mr. Mattis shrugged and told reporters with a smile: “I don’t have a problem with the press.”
Mr. Pence on Monday was asked a similar question, and while he also embraced freedom of the press, he made sure to stay close to the boss. “When the media get it wrong,” Mr. Pence said, “I promise you President Trump will take his case straight to the American people to set the record straight.”
Write to Gordon Lubold at Gordon.Lubold@wsj.com and Julian E. Barnes at email@example.com