Boris Johnson wields knife in dramatic first day as British Prime Minister

London CNN  — 

Boris Johnson, the bombastic politician who played a decisive role in the 2016 Brexit referendum, is officially Britain’s new Prime Minister.

He took office with a resounding pledge to defy the “doubters and the doomsters” by taking the country out of the European Union by the end of October – a task that defeated his predecessor, Theresa May.

Johnson’s first act was to oversee a bloodbath of Cabinet ministers. He fired supporters of his rival for the top job, Jeremy Hunt, and installed loyalists who had backed his campaign to succeed May—including his younger brother Jo.

In accordance with British constitutional protocol, he was officially invited to form a government by Queen Elizabeth II at Buckingham Palace on Wednesday afternoon, after winning the race to replace May as leader of the governing Conservative Party earlier this week.

In a rousing speech outside the famous black door of 10 Downing Street, Johnson paid tribute to his predecessor but blamed her failure to achieve Brexit on “pessimists” and “critics” who had talked Britain down. “The doubters, the doomsters, the gloomsters, they are going to get it wrong again,” he promised.

“The people who bet against Britain are going to lose their shirts,” he said, pledging that Britain would leave the EU on October 31, “no ifs, no buts.”

The Queen meets Johnson at Buckingham Palace on Wednesday.

In the following few hours, he dispatched all but one of the senior Cabinet members who had not supported his leadership bid. Hunt lost his job as foreign secretary, revealing that he had turned down another role in Cabinet, widely reported to be the less senior position of defense minister. Johnson would have his “full support,” Hunt said.

Dominic Raab, who quit his role as Brexit secretary under May’s Brexit plan last year, has taken Hunt’s place. The newly appointed Foreign Secretary was also given the post of First Secretary of State, effectively making him Deputy Prime Minister.

Chaotic moment

Known for his tousled shock of blonde hair and brash style, Johnson enters Downing Street at a chaotic moment for the UK, both at home and abroad.

Despite his Conservative Party’s flimsy majority in Parliament, Johnson has pledged to do in three months what May could not do in three years – lead Britain out of the EU, “do or die.”

Official forecasts suggest that the latter scenario – breaking out of the bloc without any deal in place – risks triggering a recession and the British pound taking a nosedive.

On Wednesday, Johnson said the UK must prepare for the “remote possibility” of a no-deal scenario. “With high hearts and growing confidence,” Britain will prepare for no deal, Johnson said. Using typically Churchillian rhetoric, he said the banks, the farms and the rest of the country “will be ready.”

Beyond the political bedlam in Britain, Johnson inherits a mounting crisis with Iran. Tehran’s seizure of a British-flagged oil tanker last week has thrust the UK into the middle of a standoff between Tehran and Washington.

All of this falls in the lap of one of the most divisive politicians of his generation, who has said much on Brexit, Iran and many other topics, but has so far divulged little about any potential plan for his premiership.

“He’s made a big pitch of re-energizing the country and bringing back optimism as a way he wants to do things,” Tim Durrant, a senior researcher at the London-based Institute for Government think tank, told CNN. “We’ll see if he has any details on the actual issues.”

Johnson, a former mayor of London and British foreign secretary, won the race to lead his party with 66% of the votes. The election was triggered after an embattled May was forced to quit after losing the support of her Cabinet, many of whom were exasperated with her inability to secure Brexit.

As Prime Minister, Johnson, 55, takes on the same problems that faced May – a deeply divided Parliament and and a fractured nation – but under even more pressured circumstances.

“Even though Boris faces the same issues that May was confronted with when she took office … the context of those issues is much different in terms of the parliamentary arithmetic and timing,” Durrant said.

Throughout his leadership campaign, Johnson was vocal about his readiness to take Britain out of the EU without a deal, pledging to leave on October 31, the latest deadline for the UK to depart the bloc.

If he cannot negotiate a new deal with the EU, Johnson has said that he’d be willing to force Brexit through on that date. He has refused to rule out suspending parliament in order to do so.

Johnson promised Wednesday to do a better deal with Brussels in less than 99 days, “because the British people have had enough of waiting.”

“I will take personal responsibility for the change I want to see… never mind the backstop, the buck stops here,” Johnson said, referring to an insurance policy designed to avoid a hard border between Northern Ireland and the Republic of Ireland.

But, given that the EU says it isn’t interested in reopening the Withdrawal Agreement – the deal that May signed with the bloc in 2018 but has been repeatedly rejected in Parliament, Johnson has his work cut out.

CNN’s Kara Fox and Rob Picheta contributed to this report.