As a world superpower, the U.S. is an impressive leader for those who will follow her, and a high-value target for those who will not.

The proliferation of what diplomats call “non-state actors,” and what the rest of us call terrorist or extremist groups, has made the job of governments and ambassadors around the world just that much harder.

The attacks Friday on the US embassy in Ankara in Turkey, a democratic country generally friendly to the U.S., once again have thrust the safety concerns of Americans abroad back onto the front page.

What makes them particularly deadly is how unpredictable they are; not just the “when” or “where,” but the “who.” While experts on Friday were predicting a connection to Hezbollah or al-Qaeda, the true perpetrators turned out to be a left-wing “Marxist” political group called the Revolutionary People’s Liberation Party/Front -- who are banned in Turkey and have been carrying out attacks against mostly Turkish officials since the 1970s -- and have rarely made an appearance in the American media or consciousness.

Sometimes our attackers are the usual suspects. Sometimes, as in Iran in 1979, what starts as a simple student protest movement turns into a full-scale crisis. Other times, little known organizations carry out attacks to get themselves on the map, as in Tanzania and Kenya in 1998, when Americans first heard the name “Osama bin Laden” for the first time after the U.S. embassies there were bombed.

From Benghazi to Ankara, throughout the years U.S. embassies all over the world have been the targets of protests and violence by terrorist groups and discontented citizens trying to make a point, or to just generally cause chaos and mayhem.

Here is a list of such incidents stretching back almost fifty years.

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