President Obama and Israeli Prime Minister Benjamin Netanyahu talk in Jerusalem in March. (Uriel Sinai/Getty Images)

In May 2010, Israeli troops boarded a flotilla of ships that had set out from Turkey for the Gaza Strip, where participants  were hoping to break the Egyptian-Israeli blockade of the Palestinian enclave and deliver humanitarian aid. Eight Turkish citizens and a Turkish American were killed in the raid -- the single worst moment in the recent deterioration of the once close relationship between Israel and Turkey.

There was this oddity from the incident and its fallout: Israeli Prime Minister Benjamin Netanyahu refused to apologize for almost three years, until President Obama personally brokered a phone call between Netanyahu and Turkish Prime Minister Recep Tayyip Erdogan this March. It was never really clear why Netanyahu had refused, for so long, to make a simple phone call that would have eased his country's relationship with an important regional player.

Well, now we may finally have an answer. Washington Post columnist David Ignatius reports on a very surprising, and until now unknown, turn in the Israel-Turkey relationship:

The Turkish-Israeli relationship became so poisonous early last year that the Turkish government of Prime Minister Recep Tayyip Erdogan is said to have disclosed to Iranian intelligence the identities of up to 10 Iranians who had been meeting inside Turkey with their Mossad case officers.

Knowledgeable sources describe the Turkish action as a “significant” loss of intelligence and “an effort to slap the Israelis.” The incident, disclosed here for the first time, illustrates the bitter, multi-dimensional spy wars that lie behind the current negotiations between Iran and Western nations over a deal to limit the Iranian nuclear program. A Turkish Embassy spokesman had no comment.

Israeli anger at the deliberate compromise of its agents may help explain why Prime Minister Benjamin Netanyahu became so entrenched in his refusal to apologize to Erdogan about the May 2010 Gaza flotilla incident.

Suddenly, Netanyahu's stance makes a lot more sense. At the time, it seemed baffling, and was widely taken as proof of the Israeli leader's self-defeating stubbornness and a reminder of the headaches that Israel can cause in Washington. This disclosure casts the refusal to apologize in a very different light, making it much more understandable.

This does not explain, of course, why Netanyahu wouldn't have apologized between the initial 2010 raid and this reported 2012 spy outing. But it gives us a hint of what the Israeli-Turkish relationship has been like behind the scenes -- not very good.

There's a larger lesson here: many developments in international relations happen in secret, with incidents like this that we never hear about. In following it as it happens, we're only seeing part of the picture. We're all working with incomplete information -- that includes heads of state as well as regular people and professional journalists and analysts -- and it can be easy to draw imperfect or outright false conclusions. Things aren't always quite what they seem.

For years, Netanyahu's failure to apologize looked rash, impudent, irresponsible -- a tantrum and a problem that the Americans had to solve for him. Now it looks significantly more rational. With time, and more revelations, it could look different again.

History is only clear, if it's ever clear, in hindsight. Without complete information, events can be difficult to understand as they're happening. So we usually fill in with personality: We say that Netanyahu got angry, or prideful. It turns out there was more to it.

Ironically, we've now got another mystery: Why did the Turkish government out these Israeli spies? We can speculate -- revenge for the flotilla raid; to secure leverage with Israel or with Iran; perhaps simply a crude reminder that Turkish support for Israel doesn't come free -- but we don't really know. That unknowability is just part of how international relations works.