Today the world will commemorate the 40th anniversary of Israel's victory in the Six-Day War. This was one of the most convincing conventional military accomplishments of the 20th century, one which removed the threat of annihilation from the Jewish States for the following four decades. 

During May 1967, Egypt's dictator Gamal Abdel Nasser and the leaders of Syria, apparently misled by carefully fed Soviet disinformation, mobilized their armies, and kicked United Nations peacekeepers out of Sinai. Nasser proclaimed "the Jews would be thrown into the Mediterranean." "Our basic objective will be to destroy Israel," he vowed May 26. 

Nasser also closed the Straits of Tiran in the Red Sea, cutting Israel's maritime link to the Far East and Africa -- a casus belli under international law. Jordan joined the pending attack, while Iraq, Saudi Arabia, Kuwait and Algeria contributed troops and arms. The shadow of the Holocaust, which had occurred little more than 20 years earlier, again descended on Israel. 

The key to Israel's victory was recognition that its was at stake. This led to full mobilization of the state and the people and creation of a government of national unity. The people and leaders had no choice but to become heroes overnight. 

A generation of brilliant generals, led by Defense Minister Moshe Dayan, was in charge of the military, ably supported by Ezer Weizmann, the former Israeli Air Force (IAF) commander and deputy chief of staff. Gen. Weizmann, the future president of Israel, and his successor, Gen. Moredchai Hod, took a huge bet by throwing the well-trained 200-strong IAF against the Egyptian Russian-trained air force. The IAF, outnumbered 3-1, destroyed the Egyptian air force in the first 45 minutes of the war. The complete air superiority of the IAF and the dogged execution of a daring battle plan designed by then Southern front commander Yeshayahu Gavish were key to the victory in Sinai. 

Meticulous intelligence work by the Mossad, led by Gen. Meir Amit, and by the military intelligence, AMAN, were also vital to attaining victory. Nasser's army in Sinai was decimated. The Jordanians, occupying Judea and Samaria (the West Bank) and East Jerusalem, and the Syrians, lodged in the escarpments of the Golan Heights, were beaten within days. 

On the diplomatic front, things were different from today. Despite blood-curdling threats by the Arab states, Israel had world public opinion largely on its side. The victory allowed Israel and the Jewish people to once again govern Jerusalem, accomplishing the dream expressed in all Jewish daily prayers during almost 2,000 years of exile. The Temple Mount, on which Solomon's Temple was built, and the Second Temple restored after the Babylonian exile, returned to Jewish sovereignty. So did the Western Wall, the most sacred site in Judaism. It is precisely the Israeli victories in the Six-Day War and in the Yom Kippur War (the failed Arab attempt at a rematch in 1973) that allowed the Jewish State to sign peace treaties with Egypt and Jordan. 

Forty years later, however, Israel's very existence is challenged again. Now more than ever, Israel is the proverbial canary in the Middle East coal mine, the litmus test of Arab and Muslim attitudes to the world beyond the Land of Islam. 

Today the threat is not only Arab -- it is also Iranian. It is not secular nationalism and pan-Arabism, but Islamist. It is both extremist Shi'a, as expressed by Iran and Hezbollah, and militant Sunni, articulated by Hamas, Islamic Jihad, Moslem Brotherhood, and increasingly, al Qaeda-affiliated organizations in Gaza and Lebanon. 

Forty years ago, the threat was classically conventional. Today, Israel and the United States lack strategy and doctrine to defeat the whole spectrum of threats, from the suicide bombings and Qassam rockets of Hamas and Fatah, to the improvised explosive devices in Iraq and the short range Iranian-supplied Katyusha rockets of Hezbollah. The threat is also unconventional -- from Syrian chemical weapons-armed rockets, to the Iranian nuclear weapons program. 

It is not the "Israeli occupation" but the rise of extremist Islamist forces that constitute a global threat and are central in Middle East destabilization. Israeli, European and U.S. policymakers and generals still think in terms of nation-states and conventional armies. The global jihadi movement, its political leaders, paymasters, recruiters and propagandists recognize no national borders. 

Israel also appears to have forgotten the lesson that in the Middle East one can negotiate only from a position of clear strength. Unilaterally pulling out of Lebanon in 2000 and from Gaza in 2005 only increased the terrorist appetite for blood. Ehud Olmert's proposed appeasement of Syria by giving up the Golan would be yet another geopolitical catastrophe. 

Leaving bloodthirsty terrorist leaders, such as Iranian President Mahmoud Ahmadinejad, Sheik Hassan Nasrallah, Hamas' Haled Mashal, or for that matter, Osama bin Laden, to roam free only delays peace in the Middle East. 

The Six-Day War teaches us important lessons in freedom. National mobilization and unity in recognition of existential threats lead to victory. Bravery and real leadership, both national and on the battlefield, secure success. Never underestimate the enemy. Intelligence matters -- and so does public diplomacy and global information support. 

Finally, we learn that both political and military institutions must recognize the nature of the evolving threat and devise and bravely carry out victorious strategies to defeat the implacable enemies of the free world, then and now.

Ariel Cohen is senior research fellow at the Heritage Foundation.