Let's not forget the Oslo Accord and its 1995 interim agreement. The PLO failed to honor the agreement. In fact, Yasser Arafat, Abbas's predecessor as PLO leader, supplied competing security organizations with thousands of weapons that were prohibited in the agreements he had signed. Again contrary to the Oslo agreement, the PLO gave its national security apparatus all the trappings of an army, which it was not permitted to have. Then in 2000, in the second intifada, it launched a terrorist attack on Israeli civilians.
Israel must prepare for the possibility that even after agreements are signed, and a demilitarized Palestinian state is established, groups such as Hamas and Islamic Jihad would act in contravention and an international force would likely not take action. Iranian-backed rocket assaults against Israel would place its coastal plain in range and make Israel uninhabitable. And if U.N. forces were present on Palestinian territory, the Israeli army couldn't open fire against the enemy without first verifying the location of the U.N. personnel. It would thus be even more difficult for Israel to act against terrorists.
There is an old saying: "Nobody ever washes a rental car." Only Israel would have the will to defend itself. When you think about the failure of NATO forces in Afghanistan, you have to wonder about the efficacy of NATO troops in this theater.
Israel knows that a threat will evolve when hostile intentions join with aggressive capabilities. Given that it has been virtually impossible to alter hostile intentions, with the split between Abbas's Fatah in the West Bank and Hamas in Gaza—the latter allowing non-state actors to emerge—classic principles of deterrence and punishment are far less effective. There is no unified government to exert control over people, weapons, and terrorist groups.
Israel has prudently maintained its uncompromising policy of disarming the terrorist infrastructure within and along its borders. But Israel's success in this relies on high-quality, precise military intelligence, along with full freedom of operation to enter Palestinian city centers and villages to locate and destroy bomb-producing factories. This is the only way that Israel can deal with the asymmetrical threat of terrorist groups able to attack Israel at will.
Until this same kind of security is assured, the two-state solution is not a solution at all, but a dramatic escalation of risk.