Berlin, Germany (CNN) -- German President Horst Koehler resigned suddenly Monday over what he said was heavy criticism about comments he made on Germany's military role in the world, which he said had been misinterpreted. It was the first time in German history that a president has resigned, the government-funded Deutsche Welle news agency reported. Koehler said May 22 upon his return from a trip to Afghanistan that "in emergencies, military intervention is necessary to uphold our interests, like for example free trade routes, for example to prevent regional instabilities which could have a negative impact on our chances in terms of trade, jobs and income."
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NEW: President's resignation is first in country's history
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NEW: Koehler had been criticized for comments on military's role
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He said comments were misinterpreted
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Resignation was sudden and unexpected
"It was an honor for me to serve @placeholder as president," he said.