[4] In his teens, after initially joining Ze'ev Jabotinsky's Betar organization, he became a member of all three Jewish underground military organizations in British-ruled Mandatory Palestine: Lehi (the "Stern Gang"), Etzel, and Haganah (Palmach) that fought the British and the Arab populations.
However, Tzabar strongly disagreed with the annexation of the Golan Heights and East Jerusalem and takeover of the West Bank and Gaza Strip by Israel in the aftermath of the Six-Day war.
In September 1967 he became famous for a declaration he published in Ha'aretz, together with 11 co-signatories, protesting against the incipient occupation.
[7] Tzabar was a columnist for a number of years for both the daily Haaretz and the weekly Ha'olam Haze newspapers.
[10] In 2004 Michelin threatened to sue him for trademark infringement, after he published a study of Israel's prisons under the title "MUCH BETTER THAN THE OFFICIAL MICHELIN Guide to Israeli prisons, Jails, concentration camps and torture chambers".