In the long weeks leading up to the Six-Day War the song "Nasser is waiting for Rabin" became popular; expressing that war was expected to break out between Israel and Egypt after the latter committed a casus belli. Israel, almost from its inception as a state, had established where its red line was: blocking its maritime trade.
Israel gritted its teeth and suffered the shutting down of the Suez Canal to Israeli ships, which violated every international treaty, up until Egypt decided to close off the Straits of Tiran as well, which it did in 1956 and 1967.
Israel responded militarily both times. In the Yom Kippur War in 1973 Egypt again tried blocking Israeli ships, but did so from off the coast of Yemen at the entrance to the Red Sea from the Indian Ocean.
The military defeats Egypt suffered each time it tried destroying Israel forced it into signing the peace treaty in 1979. The treaty was the pinnacle of President Jimmy Carter's success, and maintaining it has since been a cornerstone of U.S. foreign policy in the Middle East. The peace treaty was almost a carbon copy of the 1978 Camp David accords, which included "a framework for peace in the Middle East." Included within this framework for peace was the creation of an autonomous territory for the Palestinians in Judea and Samaria, as indeed was created (the treaty does not speak in any way of a Palestinian state), coming to a permanent solution within five years, and that the normalization of relations between Israel and Egypt would act as a precedent for striking peace deals with the other Arab countries.
Regardless, the treaty that Israel and Egypt signed included full diplomatic, economic and cultural relations. Egypt has only partially upheld its end of the deal: It has frozen diplomatic relations during crises in the region and has never met even one criterion for normalization. Moreover, Egypt has consistently violated stipulations regarding limitations to its military deployment in the Sinai Peninsula.
The only guarantee that Israel would receive an early warning about Egyptian troop movement into the Sinai would likely come from the 1,600-man Multinational Force and Observers stationed there, comprised of soldiers and officers from 12 countries, including the U.S. and Canada.
These factors, along with the fact that Israel hasn't viewed Egypt as an enemy country since the signing of the peace treaty, currently put Israel's decision-makers in a precarious position. On the one hand, Israel has thus far refrained from any action that could be interpreted by the U.S. or Egypt as an attempt to undermine or avoid its responsibilities within the peace agreement. On the other hand, a military conflict with Egypt is inevitable. The only question is the timing.
Egypt's economic situation today doesn't allow it to provide for over 85 million of its citizens. This means that a scapegoat must be found for the people to focus their rage against. The new regime will not be able to hide behind the old regime's shortcomings for very long.
What's more, every military conflict in the region has always been followed by U.S. mediation efforts, including substantial economic packages. We must not forget that U.S. foreign aid to Egypt is allocated mostly toward its military (some $1.5 billion), while some $800 million goes toward the civilian sector. This means that the U.S. is strengthening Egypt's armed forces, not its economy. Such an aid package, therefore, could very well tempt the new regime to act hastily. In light of all this, military conflict is the most reasonable possibility.
Therefore Israel must redefine its parameters for what constitutes a casus belli and notify the United States and other leading countries accordingly; the strength of deterrence lies in making your red lines known. In addition to such a public move, we should define, discreetly, our own goals.
Israel must display its commitment to the peace treaty, despite its deficiencies, practice extreme caution against being drawn into provocations and make its red lines very clear and public.
In the meantime, Israel needs to quietly prepare for any possibility — from amplifying all aspects of its military efforts to dealing with the increasingly hostile population in the Sinai — for when the day comes and the order is given.
There is no doubt that Israelis hope and wish that such a day never comes, but if it does come, God forbid, we'd better be well prepared.