With the latest war between Israel and Hamas focusing attention on civilian casualties and the subject of disproportionate violence, maybe a little history will help us understand what is happening.

So let’s start from the beginning…well, the beginning of the 20th century.

What we call Zionism today is nothing more than Jewish nationalism, not very different from nationalism elsewhere. It began when European countries became increasingly antisemitic around 1900: massacres of Jewish communities in Russia and then a trumped up charge against a French army captain named Dreyfus made antisemitism fashionable. By the 1940s, we witnessed the Holocaust.

And so many Jews came to believe that they would not be safe except in a homeland of their own.

Had that homeland existed in 1939, the Holocaust would likely have had hugely lower casualties. One tiny example: The German passenger ship "St. Louis," filled to the brim with 907 Jews fleeing from Hitler in May 1939, would have disembarked its passengers in Haifa. Instead, it was refused port access in Cuba and the USA, eventually returning to Europe where over half of its passengers would die in gas chambers.

The Zionists remember well that during the height of the Holocaust, President Roosevelt refused to open American doors to Jewish refugees. Likewise leaders of almost every other nation.

And so Israel was born in 1948, largely out of a Jewish sense of self-preservation and, by others, a sense of guilt and responsibility for what happened during the Hitler years.

Those Zionists remember something else. That when Israel came into existence, it was attacked by five neighboring Arab states that refused to accept its existence. Some Arabs, including the Palestinian Mufti of Jerusalem, had even allied with Hitler during the war. A few others, in distant Morocco and Tunisia, had provided refuge for some Jews. They were the exception, not the rule.

If you ask most Americans today about the existence of Arab hostility toward Israel, they will say "Because Israel occupies Palestinian land in the West Bank and, until recently, Gaza."

That gets it backward. In 1964, three years before the Six-Day War when the Israelis occupied the West Bank and Gaza, the PLO declared that Israel must be obliterated. Except for the Egyptians and the Jordanians after 1967, no Arab country has ever accepted Israel’s right to exist.

Nor has the situation changed fundamentally in the nearly 50 years since that war. The Hamas Charter states in its preamble: "Israel will exist and will continue to exist until Islam eliminates it…."

There’s nothing mysterious about this. The key issue isn’t Hamas’s objection to the Israel blockade of Gaza, or to Israeli settlements in the West Bank. It is to the very existence of Israel.

Israel is hardly above criticism. In 1948, the Israelis expelled over three hundred thousand Palestinians to neighboring countries. There are human-rights abuses in the West Bank. But the fundamental issue remains Israel’s existence. When Israel pulled out of Gaza in 2006, Hamas turned Gaza into a military base from which it launches missiles and sends terrorists into Israel. No state, will tolerate such acts of war.

It’s easy for Americans and Europeans, dependent on Arab oil and secure in their own homes, to damn the Israelis for using disproportionate force against their enemies. But the Israelis don’t have the luxury of playing loose with their own security. The Israelis are not suicidal, and they, unlike the rest of us, do indeed remember the history of Arab hostility that imperils their own existence.

Dr. Gary B. Ostrower has taught at Alfred University since 1969, and has been the Joseph K. Kruson Distinguished Professor. He is a former Fulbright Lecturer. He currently teaches a course at Alfred University called "Arabs, Israelis, and American Foreign Policy."