An aphorism as ancient as the Middle East itself, the borrowed title of this editorial applies to the dramatic lesson of the horrific attack by Islamic extremists on Egyptian security forces in northern Sinai.

This week saw the reports of a brutal attack by masked gunmen, described by official Egyptian sources as “Islamic extremists,” who killed 15 soldiers at an Egyptian Army base in northern Sinai. According to Monday’s edition of The New York Times, after killing the 15 Egyptian soldiers, who were preparing to break the Ramadan fast, the gunmen seized at least one armored vehicle and headed toward Israel in an apparent attempt to storm the border.

Only a timely intervention by the Israeli Air Force prevented the militants from crossing into Israel for what was believed to be another attempt to kidnap an Israeli soldier and hold him hostage. An Israeli military spokesman is quoted by the Times as having said a vehicle exploded at the border crossing, Karem Shalom, on the southern tip of the Gaza Strip. Images broadcast on Israeli TV showed an armored vehicle in flames.

While there was no immediate claim of responsibility for the deadly attack at the Egyptian Army base, Egyptian sources blamed Islamic extremists who have created a state of lawlessness in the Sinai Peninsula, which was returned to Egyptian control under terms of the Egypt-Israel Peace Treaty of 1979. Significantly, the recently installed Muslim Brotherhood-affiliated Egyptian President Mohamed Morsi, roundly condemned the attacks, appearing on television to offer his condolences to the families of the victims after he had met with senior generals and security officials.

“There’s no room to appease this treachery, this aggression, this criminality,” Morsi said. He added that the security forces would extend “full control” over the area. “Sinai is safe,” he said. Equally significant was the official statement by officials with Hamas (an offshoot of the Muslim Brotherhood), which governs the Gaza Strip, condemning the attack, calling it “terror.” They added that the tunnels that are used for smuggling between Egypt and Gaza had been closed in response to the attack.

For its part, Israel officially responded with a statement by Defense Minister Ehud Barak who said that the “attack methods again raise the need for determined Egyptian action to enforce security and prevent terror in the Sinai,” according to the Associated Press.

For Hamas in Gaza and the new Muslim Brotherhood-affiliated president of Egypt to roundly condemn the attack is a welcome change from the usual chorus of praise by Hamas and the M.B. for such terroristic actions, and their usual characterization of terrorists who carry out their missions as “martyrs.” Could it be that Hamas and the Muslim Brotherhood, now that they are officially in governing roles in Sinai and Egypt, are becoming more “moderate” or at least “pragmatic”?

It is far too early to become optimistic about the future behavior of Hamas (which was already blaming Israel for the attacks this week) and of President Morsi. But it is equally clear that the attack shows that no nation is immune from the scourge of terrorism that has wracked the Middle East for decades and shows no sign of lasting abatement.

Morsi, whose presidential powers had been substantially reduced by the military officers who are the de facto leaders of Egypt even before he took office, is walking a tightrope between the historic militancy of the Muslim Brotherhood and the need to face the realities on the ground. A previous New York Times report indicated that Morsi warmly responded to a letter from Israeli President Shimon Peres, who congratulated Morsi on his election and expressed hope for a continuation of peaceful relations between Israel and its largest and most politically important Arab neighbor. Under pressure from extreme elements in his own party, Morsi had to denounce his cordial reply to Peres as a “fake,” even though it came to Peres through official Egyptian channels.

In view of the pressures on Morsi, we should not hold our breath waiting for him to thank the Israeli Air Force for its response to the latest heinous act. But it is safe to assume that Morsi knows he has far less to fear from a peace-seeking government in Israel than from the radical regimes of Iran and the lawlessness of Islamic militants who kill their own co-religionists in cold blood when it suits their purposes to unseat civilized nations.

We hope this “wake-up call” persuades Morsi to do all within his limited power to preserve and protect the Egypt-Israel peace treaty, which has been a linchpin for stability in the Middle East ever since it was signed.