The real test that lies ahead for Ariel Sharon is linking Ma'aleh Adumim to Jerusalem by building in Area E-1. The fate of the Jewish state depends largely upon Sharon's ability to take immediate action and populate E-1 with thousands of Jews. Ma'aleh Adumim serves as the linchpin in establishing an effective line of defense along the Jordan River Valley against aggression from the East. Building a Jewish-populated corridor to Ma'aleh Adumim would prevent the division of Jerusalem and secure the only safe route via which Israel could mobilize troops from the coast to the Jordan Valley in case of emergency. Jerusalem's importance to the Jews is not only historical and religious. The city also holds strategic importance in controlling the only highway from the coast of the Mediterranean Sea to the Jordan River Valley along which Jews can travel with little interference from Arab population concentrations. OBJECTIONS TO a Jewish presence in Area E-1 express concern for Palestinian contiguity, which is a deceptive argument. Free travel between Samaria and Judea can be arranged quite easily by constructing overpasses or tunnels. (Ironically, the Palestinians suggest precisely these arrangements in response to Israeli concerns regarding the Palestinian demand for a corridor between Gaza and Judea that would divide Israel in two, as Evelyn Gordon pointed out recently in these pages.) The main issue, however, is Jerusalem. The Palestinians plan to settle E-1 with Arabs in order to create demographic contiguity between Samaria and east Jerusalem, thereby facilitating the division of the city. Such a development would also isolate Ma'aleh Adumim and undermine Israeli claims to the Jordan Valley. The only way to prevent the realization of these Palestinian plans is to populate E-1 with Jews. Some pundits claim Israel no longer needs the Jordan Valley as a shield against aggression from the east. They argue that the demise of the Saddam Hussein regime, the growing isolation of Syria and the enhanced American role in the region renders the threat of the eastern front and its proximity to Israel's centers of population and economic infrastructure a thing of the past. Yet this is a very short-term perspective, motivated by the desire to convince Israeli public opinion that the Jordan Valley is militarily dispensable. Such a view ignores the immense potential for political upheaval in the Middle East. For example, the US may decide to cut its losses and leave Iraq, which would constitute a huge victory for radical forces in the Middle East. The destabilization of Hashemite Jordan and Saudi Arabia, an emboldened radical Syria and the reemergence of the eastern front could then follow. ADVOCATES OF turning over the Jordan Valley to the Palestinians discount its topographical importance by referring to current military technology that allows precision strikes from a distance. They argue that the ability to launch defensive strikes from the coast eliminates the strategic need for the Jordan Valley as a means of defense. Yet these armchair strategists overlook the history of military technology, which shows a clear oscillation between the dominance of offensive and defensive measures over the centuries. The belief that the technology of today, which indeed temporarily reduces the importance of topography, will remain unchallenged constitutes a dangerous strategic fallacy. Designing stable defensible borders in accordance with current, but transient, technological state-of-the-art and political circumstances is strategically foolish. Therefore, if Israel wants to maintain a defensible border it needs to secure the road from the coast to the Jordan Valley, via an undivided Jerusalem and via Ma'aleh Adumim. SHARON WILL be put to the test to prove that his rhetoric about a united Jerusalem and the incorporation of settlement blocs into Israel has substance. President George W. Bush's promise to allow the incorporation of settlement blocs needs to be capitalized on in this context. Now, in the aftermath of the withdrawal from Gaza and prior to the impending Israeli elections, is probably the best time to take action. In such a political context Sharon is least vulnerable to outside pressure. We should also remember that the US has opposed Israeli settlement efforts since 1967, and only rarely did American objections have an impact on Israeli decisions regarding this issue. Moreover, the Americans can be persuaded to go along tacitly with linking Ma'aleh Adumim to Jerusalem if a clear strategic vision based upon the principle of territorial compromise is presented. While the strategic wisdom of indiscriminately settling the Land of Israel is not compelling, a selective settlement policy focusing on areas within the Israeli consensus, including Ma'aleh Adumim and the Jordan Valley, can be pursued with little foreign interference. Such a policy should be complemented with the removal of illegal outposts located outside the areas of consensus, and even with a gradual freeze in allocations to isolated settlements. Area E-1 is of vital importance for the political future of Jerusalem and for Israel's chances to establish a defensible line along its eastern border. It is imperative that homes for Jews be built there. Hopefully, Sharon will put his bulldozers where his mouth is. The author is professor of political studies at Bar-Ilan University and director of the Begin-Sadat (BESA) Center for Strategic Studies.