From The Australian:
A group of Israeli Arab women flown to Paris in 1964 were met by a Mossad officer who told them that their husbands were not who they thought they were.
“He is not an Arab,” the officer told each of them. “He is a Jew.”
As related yesterday in the Tel Aviv daily Yediot Ahronot, the story had begun a decade earlier when security officials decided to plant agents in Israeli Arab villages and towns. Israel's War of Independence, in which the newborn state battled for a year against Palestinian Arabs and the invading armies of surrounding Arab states, had ended just a few years before, in 1949. The purpose of the sleeper agents was to warn if Israeli Arabs would revolt in the event of another war.
Ten young Jewish immigrants from Iraq were trained for a year before being sent into Israeli Arab communities, posing as refugees from the war who had escaped to a neighbouring Arab country and had now infiltrated back.
It quickly became apparent that in order to maintain credibility the men would have to marry. “It would have been suspicious for young, vigorous men to remain alone, without a spouse,” said Shmuel Moriah, the security officer who headed the operation. “We didn't order them to marry, but there was such an expectation.”
More here.