LONDON — When Rishi Sunak replaced Liz Truss as British prime minister last fall, White House officials said they didn’t worry about his support for Ukraine because he left in place the respected soldier-turned-defense secretary Ben Wallace, who had orchestrated Britain’s unstinting military support of the Ukrainians.
Now Mr. Wallace has stepped down, and in his place Mr. Sunak has appointed Grant Shapps, a politically savvy Conservative Party operative and close personal ally of the prime minister, but a man with little foreign policy and no battlefield experience.
Mr. Shapps, who has held no fewer than four ministerial posts in the past year, vowed to continue the “U.K.’s support for Ukraine in their fight against Putin’s barbaric invasion.” But as Britain faces a general election in 2024, the shift from Mr. Wallace to Mr. Shapps could augur a new, more politicized phase in its involvement in Ukraine.
Conservative leaders “perceive him as one of their great communicators,” said Jill Rutter, a senior research fellow at the U.K. in a Changing Europe, a think tank in London. “It may signal that they see defense as a sort of battleground.”
Unlike in the United States, support for arming Ukraine remains strong across the British political spectrum. The Labour Party leader, Keir Starmer, pledged there would be no change in Britain’s policy toward the war if his party ousts the Conservatives, as the polls currently suggest it could.
But Ukraine could yet become a political weapon. Defense is the only major issue where polls show that the Conservatives still hold an edge over Labour among voters. Mr. Shapps, Ms. Rutter said, could press that advantage by reminding people that Mr. Starmer supported Jeremy Corbyn, a former Labour leader who once said he hoped to see alliances like NATO disbanded.
The departure of Mr. Wallace could be felt even more keenly overseas. He played a significant role in pressing the United States, Germany, and other countries to increase their military contributions to Ukraine. Mr. Shapps is less likely to do that, analysts said, if only because he does not have Mr. Wallace’s network of relationships in the Pentagon and defense ministries around Europe.
“Wallace is a hard act to follow,” said Ben Barry, a retired British brigadier and senior fellow for land warfare at the International Institute for Security Studies in London. “Acting as an international statesman and military diplomat is not something that Shapps has shown is one of his skills.”
Adding to the questions about Britain’s future role, Mr. Sunak had previously announced that he plans to skip the United Nations General Assembly in New York in September, where Ukraine is likely to be a central topic.
Mr. Shapps recently visited Ukraine as energy secretary, announcing a British loan to the country’s state nuclear energy company. On his account on X, formerly known as Twitter, he posted a video in which he viewed captured Russian tanks and gazed at bombed-out apartment towers in the capital, Kyiv.
And in a newspaper article last week, he described hosting a family of Ukrainian refugees for a year after the invasion. “I cannot emphasize enough the impact living with this extraordinary family and hearing their story has had on me and my family,” he wrote.
But he is not well known in Washington, where Mr. Wallace was a regular visitor. Biden administration officials said they valued Mr. Wallace as a symbol of continuity. Last October, he flew to Washington for urgent meetings about the war at a moment when Ms. Truss’s government was unraveling.
Still, American officials also said they viewed Mr. Wallace as quite political — a hawkish defense secretary serving a Conservative government. When Mr. Sunak floated his name to be secretary general of NATO, Mr. Biden did not offer his support, which effectively ended his hopes for the job.
Mr. Wallace held his post through three prime ministers — starting with Boris Johnson — and enjoyed the highest personal approval ratings of any cabinet minister. But there were battles between him and the Treasury over the size of increases in military spending, which Mr. Wallace generally lost.
In his resignation letter to Mr. Sunak, Mr. Wallace said, “I know you agree with me that we must not return to the days where Defence was viewed as a discretionary spend by Government and savings were achieved by hollowing out.” He added, “We both share the belief that now is the time to invest.”
Some analysts speculated that Mr. Shapps, with his close ties to Mr. Sunak and record as a political survivor, would be less likely than Mr. Wallace to tangle over budgets. They said it would take time for Mr. Shapps to master the defense ministry, one of the government’s most sprawling bureaucracies.
“Wallace was the dominant figure in setting Ukraine policy, even before the Russian invasion,” said Malcolm Chalmers, the deputy director general of the Royal United Services Institute, a think tank in London. “The balance of authority on Ukraine may shift more toward Downing Street and the foreign secretary.”
While Mr. Wallace’s departure was not a surprise — he announced weeks ago that he planned to leave the government — the choice of Mr. Shapps was. His name was not on most short lists of candidates for the post.
“I am looking forward to working with the brave men and women of our Armed Forces who defend our nation’s security,” he said in a post.
Mr. Shapps has successfully navigated an exceptionally turbulent stretch in the Conservative party and in British politics. Ms. Truss named him home secretary in the chaotic final days of her tenure. He served as transport secretary under Mr. Johnson, where he developed a reputation as an official who could adroitly defend the government on television and radio during tense moments.
A onetime web publishing entrepreneur, Mr. Shapps, 54, faced scrutiny over his business practices as well as criticism that he ignored charges of bullying by a Conservative official when he was the party’s co-chairman. He made a brief bid to be leader of the party last year, before withdrawing and endorsing Mr. Sunak.
Mr. Wallace, who served as a captain in the Scots Guards, was once seen as Tory leader material, too. But he ruled out a campaign for higher office. “That’s all folks! Been a privilege to serve this great nation,” he posted on Thursday.