Let Moshe Dayan vomit the answer (from an article he wrote back in April 1967):
"...although the Israeli Army's official title is "the Israeli Defense Forces," it is not a defensive force...the most visual manifestation of the new approach...is the lack of fortifications and fences along the borders...simply put, the Israeli Defense Forces are an aggressive offensive-minded fighting force. The Israeli military implements this approach in its thinking, planning, and Modus Operandi. [The offensive values] run in [the military's] DNA and [are] inscribed in the marrow of its bones." Cited in the lousy book, Laron, Guy, The Six-Day of War: the Breaking of the Middle East, Yale UP, p. 275).