Last week, President Obama reminded us, for a brief moment, of the difference the United States can still make in the Middle East when it leads from the front.

I refer to the president's success, during his trip to Jerusalem, in getting Israel and Turkey back on track toward normal relations. The once-close ties between the two Mediterranean powers were cut in 2010 after Israeli forces killed nine Turkish activists on the aid ship Mavi Marmara, which was trying to breach the Israeli blockade of Gaza. This dispute presented a strategic roadblock to any regional efforts to deal with Iran's nuclear program or the civil war in Syria.

Turkey wanted an apology from Israel, which needed reciprocal gestures from the Turks. Three years of backstage talks between Israeli and Turkish diplomats failed to produce a breakthrough, until Obama turned up the pressure on Jerusalem. (Secretary of State John Kerry did likewise in Ankara.)

The apology is due directly to Obama's pressure, and the success of his visit to Israel, says Alon Liel, a former head of Israel's diplomatic mission in Ankara. "Without Obama's being in Jerusalem, it wouldn't have happened," Liel stresses.

I'd go further: Obama's diplomatic achievement reveals that any hopes for regional stability still require an America willing to lead.

Consider the history of the break between Turkey and Israel. Their relations had already begun their sharp slide after the 2008 Israeli invasion of Gaza. The attack ended personal efforts by Turkish Prime Minister Recep Tayyip Erdogan to restart peace talks between Israel and Syria. He told me in a 2009 interview that he was further upset by Israel's refusal to let Turkey deliver relief supplies to Gaza.

The Mavi Marmara deaths infuriated Erdogan, who insisted on an apology and an end to the blockade. Meanwhile, Israelis were outraged that the Turkish leader never criticized rocket attacks on Israeli towns by Hamas from Gaza. Yet, backstage, Israeli and Turkish diplomats - aware of the strategic importance of their past ties - kept trying to negotiate.

In July 2011, Israeli and Turkish sources told me that a compromise was near. They said Prime Minister Benjamin Netanyahu was considering an apology for "operational mistakes" during the raid (the very formula he used last week). Then Defense Minister Ehud Barak endorsed the idea. Still nothing happened.

In September 2011, a U.N. commission on the Mavi Marmara incident provided cover for the apology. The commission's report recognized Israel's right to impose a naval blockade on Gaza in order to prevent arms shipments to Hamas, but concluded that the Israeli raid had used "excessive force."

Given the claims by many parties, including Turkey, that the blockade itself was illegal, the U.N. findings were a boon for Israel. All expectations then were that the apology would be forthcoming. Yet, for domestic political reasons, Netanyahu pulled back.

Since then, repeated efforts by U.S. diplomats to end the dispute led nowhere - until Obama decided to apply some muscle. Kerry did the same in Ankara, pressing Erdogan to walk back inflammatory language about Zionism and soften added demands on Israel, beyond the apology.

As Obama was leaving Jerusalem, Netanyahu finally made the call from a trailer parked on the Ben Gurion airport tarmac. Under insistent prodding from Obama, the deal was finally closed (although more details must be worked out before the sides normalize diplomatic relations).

Yet the efforts the president made to achieve a breakthrough in Israeli-Turkish relations raise perplexing questions about his wider approach to the Middle East.

After all, Obama's push to restore ties between Jerusalem and Istanbul was based on hopes that they could provide a strategic anchor to a region dissolving into ever greater chaos. Yet the president has famously chosen to "lead from behind" on Syria (not to mention Iraq and the peace process).

Obama has outsourced military aid to Syrian rebels to Gulf states, which inevitably has led to the strengthening of radical Islamists inside the country at the expense of non-Islamists. Meantime, Syria is collapsing: The war's spillover is destabilizing Lebanon, Iraq, Turkey, and Jordan - and threatening Israel.

America's closest European and Arab allies - as well as Turkey - have been desperately looking for signs of U.S. leadership on Syria, yet Obama has appeared paralyzed. U.S. attempts to promote a diplomatic solution to the Syrian crisis have proved unrealistic. American efforts to back an inclusive and moderate Syrian civilian leadership have failed to provide the necessary support.

If Obama's goal in restoring Israeli-Turkish ties is to help stabilize the region, it will have to be part of some larger strategic plan that looks at the bigger picture, especially Syria. The president's show of leadership in thawing those ties was indeed impressive, but it won't have much impact on the region unless he replicates it on a wider scale.

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