This is it.



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Note added at 14 hrs 34 mins (2006-01-09 16:56:54 GMT)
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Apparently, and contrary to what I had speculated in my note to Eynati, the expression has nothing to do with Trumpeldor. Instead, it arose following the Holocaust as an expression of Jewish determination to build, and successfully defend, a state of their own because, in terms of collective survival, "there was no alternative".

Here is a reference, from http://www.ou.org/torah/grossman/2004/022704.htm:

After the Holocaust, most of world Jewry said, 'Ein Breira,' there is no alternative. And in 1948, Israel, the Jewish State, was born. On that day, the Arabs, rejecting the United Nations plan for land partition into two states, one Jewish, one Arab, went to war. The Arabs continued to aggressively attack in full-blown wars and wars of attrition. In 1964, the Palestine Liberation Organization was created by the KGB. The Soviet Union's concern had nothing to do with whose land it was, but their support for a revolutionary Arab movement was designed to destroy the Jewish State, which provided the Americans a foothold in the energy rich Middle East and hegemony in that all important region.