Not that long ago, when it came to global security issues, France often went its own way, taking no part in NATO's military command and often at odds with the Americans.

Not anymore. Today, France is a key player in NATO's military structure and has taken a leading role in Europe on issues in North Africa and the Middle East. And thanks to a surprising vote last week in the British Parliament not to back military action in Syria, French President François Hollande has pushed aside British Prime Minister David Cameron to become the United States' new best friend.

Mr. Hollande is "the last man standing in Europe so to speak. He's the go-to guy," said Rem Korteweg a senior research fellow at the Centre for European Reform in London. The French President "is opportunistic and he's willing to seize the moment to show himself as the unquestioned leader of Europe on defence and security issues. … I definitely think that larger geopolitical considerations are at the back of Hollande's mind."

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None of this is by accident. France has spent six years re-establishing its ties with the U.S. and taking on a greater role in Europe.

It began within days of the election of Nicolas Sarkozy as president in May, 2007. A conservative, Mr. Sarkozy immediately changed the tone in France's relationship with the U.S., which had sunk to a low in 2003 when France vigorously opposed the invasion of Iraq. That caused outrage in the U.S. with many Americans buying "freedom fries" and pouring French wine down sewers.

"I want to call out to our American friends to tell them that they can count on our friendship," Mr. Sarkozy said within hours of his victory. A couple of months later, he took his first vacation as president – to New Hampshire.

He also had this to say to his countrymen: "France is back in Europe."

By 2009, France had rejoined NATO's military command, after a 40-year absence, and was soon leading the charge against Libya's Moammar Gadhafi.

Mr. Hollande, a socialist, defeated Mr. Sarkozy last year, but he shares many of the same views on foreign policy. Before becoming president, he supported the air attacks on Libya and joined in Mr. Sarkozy's condemnation of the Syrian regime of Bashar al-Assad.

Earlier this year, he sent French troops into Mali to go after al-Qaeda-backed rebels who were trying to overthrow the government. The military action was largely a success and France won praise from the U.S., Britain and other European countries for taking on terrorism.

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Mr. Hollande also became one of the first advocates for military action against the Syrian government for allegedly using chemical weapons and he was among the first world leaders to recognize the Syrian National Council as the legitimate representative of the Syrian people.

Another key change came last May, when the French government released a sweeping review of its defence strategy. For months, there had been speculation Mr. Hollande would slash military spending, given the country's weak financial condition. While some spending was cut, along with military personnel, the cuts were not nearly as deep as many expected. More importantly, the "white paper" outlined a new emphasis in France's foreign-policy interests.

The paper observed that the U.S. is switching its attention toward Asia and retrenching from North Africa and the Middle East, opening up an opportunity for France to take a leadership role in this area.

France has always had a keen interest in the region. It was French and British diplomats who carved up the Middle East into spheres of influence in 1916 and France has always had a connection with Christians in the area. "As the United States pivots eastwards, France sees itself (and Europe) as increasingly responsible for taking the lead in providing security to this [area]," Luis Simon, a researcher at the Institute for European Studies in Brussels, wrote in an analysis of the French policy.

Some question Mr. Hollande's new aggressive stand on Syria and his attempts to push France into a more active position in Europe.

France cannot act alone on Syria and if the U.S. backs out, Mr. Hollande could end up looking weak given that no other European country supports a military strike, said Vivien Pertusot of the French Institute of International Relations. "France is maybe the leader of Europe by default but I'm not sure the rest of the European countries see France as the leading power of the Europe that they want," Mr. Pertusot said.