Sixty-five years after Germany's campaign to exterminate the Jews, of the many countries in the world Israel is the only one repeatedly subjected to calls for its extinction. Though Pakistan and India, like Israel and the Arabs, suffered population exchange and territorial wars, neither questions the other's right to exist. So rare and extreme is such a position that one might think the countries of Europe, so many of which cooperated in hunting down their Jews, would do more to recognize its endemic presence in the Middle East.

They don't—their publics having largely accepted that, in regard to the question of Palestine, Arabs were victims and Jews victimizers and colonialists to boot, even though the Jews had no mother country and it was their armed struggle that ejected Britain from the Levant. Conveniently forgotten is that the Jews accepted partition and the Arabs did not; that half the Palestinians who left in 1948 did so of their own volition; that more Jews left and were expelled from Arab countries than Arabs left and were expelled from Palestine; that Arabs were able to remain in Israel whereas the Arab states are effectively Judenrein; that Israel ceded the Sinai for a paper treaty, and Gaza in return for nothing but rockets and bombs; that, amidst a sea of Islamic states, it has accepted a Palestinian state while the Palestinians indignantly refuse to recognize it as a Jewish state; and that it was ready to compromise even on Jerusalem had Yasser Arafat been willing to take yes for an answer.

Conveniently forgotten in fallacious references to a "cycle of violence" is that—following from their oft-stated call for the destruction of Israel—Hamas, Hezbollah (which is more or less an Iranian expeditionary force), Iran itself, and the Arab confrontation states are the parties that want to change the status quo, by violence and by their own flamboyant admission.

In many quarters, all this has been swept aside by the conviction that as long as the Palestinian refugees from Israel (unlike the greater numbers of their Jewish counterparts from Arab lands) remain unassimilated, and as long as their flag does not fly from the Mediterranean to the Jordan, they are the underdog. Of course, the underdog is not always right; nor are the Palestinians, backed by the power of the Arab states and Iran, exactly the underdog.

The popular view of Israel as a "regional superpower" that at little cost to itself rolls over its opponents has for decades been sustained by Arab propaganda, Western antisemitism, and Israeli braggadocio. It exempts those who subscribe to it from the burden of knowing the orders of battle and the geography and history of the conflict, and—in regard to Israel's ongoing casualties or in the event of its destruction—serves as a preset moral salve.

But Israel has seldom gotten off easily. In 1948 it had 30,000 casualties, including 6,000 dead, which given its population was proportionally as if today 2.6 million Americans were killed, more than all the deaths in all the wars in our history. In 1967, in just six days of battle that created the legend of its invincibility, the proportional figure is 118,000 dead, 20 times the number of Americans killed in Iraq and Afghanistan since 2001. The numbers for the subsequent War of Attrition are much the same, higher for the October War of 1973, and civilian and military deaths continue even through relatively peaceful interludes.

In 1973, having overwhelmed the Bar-Lev Line, crossed the Suez Canal, downed a significant portion of the Israeli Air Force, and penetrated deep into the Sinai, an elated Egyptian army found itself with virtually nothing between it and Israel's heartland. The accepted narrative is that the Egyptians could not conceive of going forward, were frightened, and had insufficient supply. But they had fought in Israel in 1948, and sat on the border for all but six years since. Having beaten back the Israelis, they were anything but frightened, and their lines of supply were adequate. But knowing that had they continued, their concentrations of armor would have been vulnerable to tactical nuclear weapons, that if Israel's existence hung in the balance so would Cairo's and Alexandria's, and that the whole of Egypt could drown in the flood of a breached Aswan Dam, they went no farther.

Partly as a result of the steady development of Saudi air power in response to Iraq and Iran, Israel's potential antagonists are closing the gap in numbers and quality, and the Israeli Air Force does not offer the same margin of safety that once it did. With the Arabs' approaching 1.3:1 advantage in first-line aircraft, 2.9:1 in second-line aircraft, and an enormous 12:1 advantage in mobile air defense, many new options open if the Arabs coalesce as they did prior to the three major Arab-Israeli wars, in each of which Israel's existence was at stake and the result unpredictable. If Turkey is included, as it might be, Israel's prospects become seriously darker. In light of the fact that the conventional balance can change and is changing, one of the many purposes of Iran's drive for nuclear weapons is not merely to wait for a lucky shot at Tel Aviv, but to neutralize Israel's nuclear deterrent so as to allow a series of conventional battles to advance Israel's downfall incrementally.

The military grand strategy of Israel's enemies is now to alter the conventional balance while either equipping themselves with nuclear weapons or denying Israel its own. Their calls for equation of the two sides in a nuclear-free Middle East leave out the lack of equation in aims. Israel cannot dream of conquering its adversaries and replacing them with a Jewish state. But from war to war its adversaries have made their intentions clear, and as their mass and wealth are applied to their militaries over time, Israel's last line of defense in a continual state of siege is the nuclear arsenal devoted solely to the preservation of its existence.

* * *

A version of this essay appeared in the Wall Street Journal.