WASHINGTON -- Britain has traditionally been considered the U.S.'s closest friend. Now it may once again be one of its most assertive.
British Prime Minister David Cameron won strong parliamentary approval on Thursday to go to war in Syria, joining a U.S.-led coalition that is targeting territory there controlled by the Islamic State group. Four British bombers hit the group in Syria hours after the vote.
Parliament's polarizing decision, settled with the support of Cameron's party and one-third of the members of the opposition Labour party, came a week after the British government made clear that it was prioritizing national security spending across the board. Cameron announced on Nov. 23 that he plans for Britain to spend $269 billion on defense over the next decade -- increasing equipment spending by $18 billion and its counterterrorism spending by 30 percent, and increasing its number of rapid strike brigades and fleet of maritime patrol planes.
"Having got the economy largely under control, consolidated the recovery after the meltdown of 2008, we are now in a position to do a bit more in terms of resources about our national security," Ambassador Peter Westmacott told HuffPost in an interview the day of Cameron's defense spending announcement.
In a 2010 defense review following the financial crisis, Cameron slashed the armed forces budget. Britain is no longer where it was back then: It had the world's fastest-growing major economy last year, and it may retain that title for 2015, Reuters reported. Cameron, who won re-election in May, says ramping up Britain's military capacity following this improvement is a key test of British credibility -- a sign that Washington should continue to value the United Kingdom's role and that the country is willing to play its part in confronting global threats.
"We can now do the things that we think are necessary to look after our national security in an increasingly dangerous world," Westmacott said.
The prime minister was unable to win parliamentary support for an attack on brutal Syrian President Bashar Assad in 2013 after Assad appeared to have used chemical weapons to kill hundreds of his own people, but Cameron did secure approval for a British air campaign over Iraq last year. Westmacott and other British officials described extending that campaign into Syria as a logical and necessary step given that that country is the extremists' hub.
Anti-war protesters have challenged this rhetoric, citing casualties that may result from British strikes, and comparing Cameron's push for U.K. involvement in Syria to Britain's support for the U.S.-led invasion of Iraq in 2003, which helped the Islamic State group rise to power in the first place.
The ambassador said Britain's renewed focus on its military had to do with concerns beyond those linked to the Middle East, including the need for stronger intelligence-gathering capabilities, European security following Russia's intervention in Ukraine and territorial defense.
"A lot of people are up to a lot of no good along the shores of the United Kingdom these days," Westmacott told HuffPost, an apparent reference to recent Russian flights and submarine patrols around the island. Britain has had to seek American and French help in detecting Russian submarines because the 2010 review ended the U.K.'s spending on submarine-tracking aircraft.
The U.K. will also use its increasing capabilities to work against homeland terror threats linked to the Islamic State group -- it says it has already foiled seven such plots -- and largely overlooked concerns such as piracy in Somalia.
"It's about making sure that the U.K. is in a stronger place to work alongside its partners and allies to try to make the world a safer place," Westmacott said. "We need to be in a position to deploy at short notice to a number of different places."
Watch his full remarks on Britain's military plans above.
This story is part of the third installment in The Huffington Post's "Diplochats" series, which interviews prominent diplomats on important global issues. (Note: The series was previously known as "Ambassadors Unplugged." Past stories in the series can be found here.)