Smoke rises after an attack of Israeli aircraft in the Gaza Strip on Tuesday. (Mohammed Saber/European Pressphoto Agency)

What happens when hopes for a negotiated settlement of the Israeli-Palestinian conflict collapse? We have been watching the answer over the past month, as extremist killers drive events and Palestinian rocket attacks beget Israeli rockets in retaliation. The fact that it was so predictable makes it all the more horrifying.

For Secretary of State John Kerry, who was mocked over the past year for putting so much stress on the peace process, recent events must have a sickening resonance. As Kerry and his chief negotiator, Martin Indyk, have learned so painfully, this is a conflict that the United States must attempt to solve but cannot solve.

Some may argue that Kerry himself set the stage for this latest explosion of violence, by raising expectations that could not be fulfilled and, in the process, deepening the divisions and mistrust on both sides. He was rubbing a raw wound, it will be said, and now the fragile scar tissue has burst open in violence.

What’s indisputable is that Kerry has been warning for a year that a failure of the peace process could lead to violence. I asked the State Department on Tuesday to gather some of his comments, which make chilling reading on a day when Palestinians fired about 160 rockets at the Jewish state and Israel retaliated with its own missile attacks and an offensive called “Operation Protective Edge.” Here’s a sampling:

“What is the alternative to peace? Prolonged, continued conflict. The absence of peace really means you have a sort of low-grade conflict, war.” Kerry said that back in November 2013, in a press conference in Jordan.

“I want you to consider what happens if the talks fail. … Failure will only embolden extremists and empower hardliners at the expense of the moderates who have been committed to a nonviolent track to try to find peace.” Kerry said that on Jan. 24. A week later, he argued: “Today’s status quo absolutely, to a certainty, I promise you 100 percent, cannot be maintained. It’s no sustainable. It’s illusionary.”

Less than two months ago, on May 29, with the peace process in ruins, Kerry said: “My reality check tells me that neither side is going to be able to live for the long haul with the status quo without serious problems evolving.”

What’s disturbing, most of all for thoughtful Israelis and Palestinians, is that this crisis could be seen developing in slow motion. It didn’t sneak up on anyone. It was predicted, over and over.

The most difficult question now for Kerry is whether he has the credibility with either side to help rebuild dialogue after this new war in Gaza. He should be careful about reentering this fray. The cruelest outcome would be if his peace process proved so unsuccessful that it killed the very idea of a U.S.-mediated settlement.