"Big mistake made all over Europe in allowing millions of people in who have so strongly and violently changed their culture!" the president wrote on Twitter.
"It's no longer the case that the United States will simply just protect us," Merkel said at an award ceremony for French President Emmanuel Macron.
Syria has been ravaged by a bloody civil war for the past seven years.
Germany may soon implement a gender-neutral national anthem after a government commissioner on equality called for the removal of "fatherland" from the lyrics.
The German chancellor said it was "shameful" Berlin still needed to allocate special police resources to protect Jewish institutions.
Russia is reinforcing its forces in Crimea by dispatching more S-400 surface to air missiles there.
Arthur Wagner's departure has caused a minor media sensation.
Ukraine's future is no longer a binary struggle between a pro-Western and a pro-Russian future. Now, China's in the mix.
Chinese Army aircraft may approach Taiwan under the guise of commercial airliners.
Ukraine's security service has brought criminal charges against leading reform groups.
Three important things to know about China's burgeoning military policy.
Does Trump have the necessary perseverance and thoroughness to challenge Xi?
The German chancellor had to tell the president she needed the other 27 members of the European Union to make a trade deal with the U.S.
U.S. military forces in Europe are busily repainting their desert tan equipment in forest green.
The EU cannot afford to become indifferent to threats to the rule of law among its members.
China may ultimately prefer Ukraine to be in Russia's orbit rather than the West's.