One of the excuses offered by Israel's government for it's continued occupation of territories outside it's pre-1967 borders is that this is necessary for the nation's security because the original borders were not "defensible".
There are some objections to this on factual grounds, which I think deserve to be more widely read...
Israelis Differ on ‘Defensible Borders’
by Robert Mackey, May 27, 2011
The ongoing dispute about whether or not it is permissible for supporters of Israel to even refer to the country’s 1967 borders as one element in future negotiations with the Palestinians obscures the fact that some Israelis disagree strongly with Prime Minister Benjamin Netanyahu’s view that a country with those frontiers would be 'indefensible.'
Netanyahu is bad for Israel,
May 22, 2011:
Netanyahu’s claim regarding the non-defensible 1967 borders was true prior to 1967, it is nothing but hogwash today. In the 1960’s when Israel was a young state without the military might that it has today an argument could be made that there was in fact an existential threat to Israel from its neighbors who refused to recognize Israel, negotiate or make peace. The narrow neck of Israel 14 miles wide between Tulkarm and Netanya was a point where the country could have been cut in half. There was a formidable Jordanian army with an air force and artillery. The Jordanians put their army under the command of the UAR of Egypt and Syria in 1967.
Former Israeli diplomats in Washington: 1967 borders are defensible by Natasha Mozgovaya, Jul. 25, 2011, Haaretz
The former ambassadors and decorated soldiers met with U.S. National Security Council in Washington with an appraisal of Israel's security needs significantly different from the prime minister's. ... A group of former Israeli army officials and diplomats visited Washington Monday, claiming that a peace agreement with the Palestinians is urgent in spite of, and because of, regional turmoil, and that contrary to what Prime Minister Benjamin Netanyahu claims, the 1967 borders are, in fact, defensible.