BERLIN — Guido Westerwelle, a former German foreign minister who strongly advocated a ‘‘culture of military restraint’’ and shunned NATO’s military intervention in Libya in 2011, died Friday. He was 54.
Mr. Westerwelle was diagnosed in June 2014 with acute leukemia. His Westerwelle Foundation said on its website that he died at a Cologne hospital Friday of complications related to his treatment. Alexander Vogel, the head of Westerwelle’s office at the foundation, confirmed the death.
Mr. Westerwelle became foreign minister and Chancellor Angela Merkel’s deputy in 2009 after leading his probusiness Free Democratic Party — post-war Germany’s traditional kingmaker — to its best-ever election result and ending an 11-year spell in opposition.
A skilled party politician and opposition leader, Mr. Westerwelle wooed voters with pledges of big tax cuts. But he was unable to push those through after entering Merkel’s government, and his party’s popularity slumped as it was blamed for frequent coalition infighting.
Even as Germany showed an increasing willingness to exert its financial clout as Europe struggled through its debt crisis, Mr. Westerwelle reinforced the country’s traditional reluctance to be drawn into military deployments abroad.
In 2011, Germany decided against taking part in NATO’s military campaign in Libya and also abstained in the UN Security Council vote that authorized the mission — a move that set it against its traditional Western allies.
While there was little appetite at home for engaging in military action, and turmoil in the years after dictator Moammar Gadhafi’s overthrow offered ammunition to critics of NATO’s limited campaign of airstrikes, Germany’s diplomatic handling of the matter prompted widespread criticism. Still, Mr. Westerwelle wasn’t deflected from his approach.
‘‘The culture of military restraint is more timely than ever,’’ he said in 2012. ‘‘I am concerned about a neo-bellicism which awakens the impression that it is possible for military interventions to be faster, more effective and ‘surgical,’ or without civilian victims.’’
During Mr. Westerwelle’s tenure, Germany participated in six-power talks with Iran, which shortly before he left office produced the interim deal that saw Tehran freeze or curb various nuclear activities in return for a limited easing of sanctions.
In Europe, Mr. Westerwelle supported Merkel’s austerity-heavy approach to tackling the continent’s debt crisis, though he voiced concern about the nastiness of some politicians’ rhetoric on both sides of the argument.
‘‘The tone of the debate is very dangerous,’’ he said at the height of the crisis in 2012. ‘‘We must take care not to talk Europe down.’’
Mr. Westerwelle became the Free Democrats’ leader in 2001 and sought to freshen their stuffy image. Still, a much-mocked 2002 election campaign in which he toured Germany in a bright yellow bus dubbed the ‘‘Guidomobil’’ ended with poor results for the party, and he subsequently cultivated a more sober, statesmanlike image.
Mr. Westerwelle publicly came out as gay in 2004, when he brought his partner, Michael Mronz, to Merkel’s 50th birthday party. ‘‘I have never lived my life in the closet — I just didn’t put in the shop window. I lived it normally,’’ he later said.
Mr. Westerwelle’s tenure as party leader and vice chancellor ended in early 2011, though he remained foreign minister. He quit the party job after a string of dismal regional election results. Successor Philipp Roesler failed to turn around the Free Democrats’ fortunes and they were voted out of Parliament for the first time in 2013.
After leaving government, Mr. Westerwelle set up the Westerwelle Foundation, an institution that aims to strengthen democracy by promoting economic development.
In November, Mr. Westerwelle published a book on his experience after his leukemia diagnosis, titled ‘‘Between Two Lives.’’
The current foreign minister, Frank-Walter Steinmeier, said Mr. Westerwelle ‘‘stands for an open, liberal Germany’’ and was ‘‘a true patriot.’’
‘‘Guido Westerwelle was always a fighter, including in his last battle, which he lost today,’’ Steinmeier said.