"Peace between the two countries has been, and still is, an interest common to both peoples," read the condolence message from Israel's Foreign Ministry to Egypt after the attack on the border this week. Indeed, we have a key common interest in rooting out terror from the Sinai. This week's tragedy has led to what neither Israel nor Egypt dreamed would happen since the signing of the Camp David Accords in 1978.

Israel has allowed Egyptian fighter jets to enter Sinai air space to strike terrorist bases as part of the new Egyptian regime's campaign, and the world has not come to an end. Egypt has not taken advantage of the situation to flex its muscles at Israel; it does not see the move as a precedent to take advantage of. To Egypt, as to Israel, which acted wisely, the move was an inevitable necessity if the two countries seek to fight a common threat seriously.

Both Egypt and Israel realize that the reality in the Sinai that dictated the peace agreements has changed. The threats now did not exist then. So with or without agreements, the two countries made the right decision this week; it was the latest achievement of the peace with Egypt.

Considering the political conditions in Israel and Egypt, such a decision isn't obvious. Israel's concerns about the Muslim Brotherhood's regime and the Brotherhood's revulsion for Israel could easily tear apart the flimsy peace.

Many people in Egypt are calling for the Camp David Accords to be changed so that Egypt can fully realize its sovereignty in the Sinai. The Egyptian president, the Brotherhood's Mohammed Morsi, has rejected these demands and has vowed to honor the agreements. When the test came this week, we may note with satisfaction that the peace treaty, cold or freezing though it may be, has fulfilled its purpose.

The two countries recognize the importance of their cooperation and the need to strengthen Egypt's control over the Sinai. Israel should extend its military cooperation anywhere it can strengthen its alliance with its neighbor.