Israel has been cautious in Lebanon, fearing not only for the lives of its soldiers, but also that an overly aggressive military campaign will alienate world opinion and force its hand diplomatically at the UN. However, Israeli leaders ought to worry more about a different scenario, one in which American policymakers, analyzing the Israel Defense Forces' failure to defeat Hezbollah after 30 days effort, lose their faith in Israel's ability to "get the job done" on issues of shared strategic interest.

Should the IDF lose its aura of invincibility in American eyes, Israel's perceived value as an ally could decline sharply. This reassessment in Washington, when combined with a continuing and even heightened determination by Arab states and jihadists to destroy Israel, would be catastrophic for its security.

For decades, Israel has enjoyed an extremely close relationship with the United States. These ties have grown even stronger during George W. Bush's presidency. Israeli leaders should not, however, take American support for granted. There is, of course, a tremendous reservoir of good will and genuine affection for Israel among Americans; but sentiment and habit alone are not a sufficient basis for an enduring U.S.-Israel alliance. The hard truth is that Israel must appear to be, and be, a winner in order to remain a valuable strategic partner for the United States.

As Israel's leaders once understood, the Washington-Jerusalem strategic partnership has always been nurtured by a steady stream of Israeli successes, both in defending its own security and in advancing American interests. These successes ranged from humbling the Soviet Union's Cold War Arab clients, proving the superiority of America's weapons over Russia's (the IDF's 1982 downing of 85 Syrian MIGs being a perfect case in point), to providing invaluable intelligence and being a democracy in a sea of autocracies.
Israel's successful 1981 Osirak mission was another excellent example of its strategic value in the Middle East. An Israel that could defang Saddam's nuclear program could also credibly offer the United States help against Iran's looming nuclear threat.

By contrast, Israel's inability to defeat Hezbollah, at least at the tactical and operational level, makes it look less like a valuable ally and more like a liability. This is particularly the case because of the impact - well understood in Washington particularly in the post-September 11 environment - of Arab perceptions of Israeli strength or weakness on their assessment of U.S. capabilities. The Bush administration's pro-democracy strategy also makes it far more difficult for it to ignore the stridently anti-Israeli views expressed by the proto-democratic governments in Iraq and Lebanon.

The fact that the United States has spent major diplomatic capital providing Israel with an unprecedented window of opportunity to deal with Hezbollah, facing down both its European allies and the Arab League, and complicating efforts to launch multilateral sanctions against Iran, makes matters even worse.

This is especially true when U.S. domestic political developments are taken into account. In the past, Israel could depend upon a basic consensus among both Republicans and Democrats that it was a valuable, indeed indispensable, ally that occupied the moral high ground. The political sands, however, are shifting. Anti-Israeli sentiments are rife among Democrats - 59 percent want the U.S. to be more "evenhanded" in the Middle East - some of whom appear to be convinced that the Bush administration's deposition of Saddam Hussein was masterminded by "neo-conservatives" in Israel's interest.

Senator Joseph Lieberman's August 8 loss in the Connecticut primary, and the evident triumph of the Democrats' neo-McGovernite wing, signal trouble ahead.

The danger posed by Israel's flawed assessment of its closest friend is matched by its apparent neglect of its enemies' evolving nature. For all of its long experience of the neighboring secular Arab dictatorships, Hamas, and even Hezbollah, Israel has relatively little experience with full-scale jihadi warfare that fuses religion, authoritarian state power, and a pan-Islamic alliance of radical groups. Obviously, this is also true of the United States and the West in general, but Israel has far less room for error.

Organizations like Hezbollah, Al-Qaida and Hamas are not just committed to Israel's destruction at the rhetorical level - as a means of palliating restive populations - but are actively pursuing this objective as a near-term goal, and Hezbollah's ability to hold its own against the IDF has reinforced the Islamists already ebullient mood.

The radical Islamist belief that the West is a "weak horse" has, of course, also been reinforced by the continuing insurgency in Iraq and the rising peace movements in Europe and the United States, but Israel is on the front line. Any conclusion of the current conflict on terms that leave Hezbollah unbowed would further undercut the West's credibility, and would squander much of the deterrent effect of Israel's past military successes from 1948 to the present.

In short, Israel must win.

The writers, who served in a variety of legal and policy positions in the U.S. government, are partners in the Washington D.C. office of Baker & Hostetler LLP and are also members of the UN Subcommission on the Promotion and Protection of Human Rights