He became known for crossing the lines during the Siege of Beirut to meet Yasser Arafat on 3 July 1982, the first time the Palestinian leader met with an Israeli.

Avnery was the author of several books about the Israeli–Palestinian conflict, including 1948: A Soldier's Tale, the Bloody Road to Jerusalem (2008); Israel's Vicious Circle (2008); and My Friend, the Enemy (1986).

Avnery was born in Beckum, near Münster[5] in Westphalia, as Helmut Ostermann, the youngest of four children, to a well-established German Jewish family, his father being a private banker in the town.

[5] However, unlike his comrade-in-arms Yitzhak Shamir who joined up at roughly the same time, Avnery was judged too young to engage directly in actions[13] such as killing Jews suspected of being informers for the British authorities, and bombing Arab markets.

[5] He changed his surname to Avnery, a Hebraic rendering of Werner,[14] to honour the memory of his only brother, who died serving in the British Army in Gondar on the East African front in 1941.

[12] When Avnery was 16 years old, the Second World War broke out; it sparked in him a lifelong interest in military strategy, which he started studying in order to better follow events at the time.

Avnery abandoned Zionism at an early age, while remaining a nationalist, which he regarded as a natural feeling for desiring to belong to a collectivity, legitimate for Jews as it was for Arabs.

[19] This "Semitic region" where he envisaged an alliance between Arab and Jewish national movements included Palestine, Transjordan, Lebanon, Syria, and Iraq.

[20] In 1947 Avnery founded his own small group, Eretz Yisrael HaTze'ira ("Young Land of Israel"), which published the journal Ma'avak ("Struggle").

[22][10][23] He wrote dispatches from the front line which were published in Haaretz and later as a book, In the Fields of Philistia (Hebrew: בשדות פלשת, Bi-Sdot Pleshet).

[5] Avnery was wounded twice, the second time, toward the end of the war, seriously; he spent the last months of his army service convalescing and was discharged in the summer of 1949.

[22] Avnery edited the weekly magazine, with its banner maxim "without fear, without bias,"[24] during the 1950s and the 1960s, turning it into an anti-establishment tabloid known for many sensational scoops.

He was arraigned on charges of sedition, survived two assassination attempts, and, in 1953, an unknown person—in one version he states that soldiers were involved[27]—assaulted him, leaving him with both hands and all his fingers broken.

[28] Avnery introduced a punchy, aggressive style of newspaper writing into Israeli journalism and, according to Greer Fay, virtually every journalist who trained under him moved on to become a star elsewhere.

[26][24] The move was inspired by the passage in 1965 of a Law against Defamation in Israel, which Avnery took personally as a legislative measure designed to muzzle his newspaper's reportage.

[32] By the 1970s, Avnery came to think that Zionism—an ideology centered on the ingathering of the exiles—was effectively dead, since diaspora Jews in significant numbers were no longer performing aliyah.

[5] In her will, Hilda wrote "I do not leave a penny to my son Uri, who instead of taking care of me went off to visit that murderer Yasser Arafat".

Around 1951, they crossed paths again when a director of a theatrical troupe introduced her as a possible choice for a photograph required for an ad his magazine intended to run.

They formalized their relationship privately with a rabbi to set Rachel's father's mind at rest when the latter fell ill.[27] Avnery said her outstanding trait was empathy, something he illustrated by an anecdote of watching a film[a] concerning an old woman in the Slovak Republic who does not understand a deportation order, and neighbours assist her in going to the assembly point for departure to the death camps.

[27] The gesture of kissing her on the brow was repeated by Yasser Arafat when she and her husband acted as human shields when he was under siege and holed up in the Mukataa.

[27] She earned the respect and friendship of Raed Salah during tent protests against Yitzhak Rabin's deportation of 415 Palestinians to Lebanon in December 1992.