SADEH (Landsberg ), YIẒḤAK (1890–1952), creator of the *Palmaḥ and its first commander. Born in Lublin, Poland, Sadeh served in the Russian army in World War i and was decorated for bravery. He continued to serve in the Red Army, where he commanded the first company of the first battalion. After the war he enrolled at the University of Simferopol, Crimea, studying philology and philosophy, and became a champion wrestler and weight-lifter. A meeting with Joseph *Trumpeldor, which took place in 1917, had a profound influence on the course of Sadeh's life. In 1920, when news reached him of Trumpeldor's death in action at Tel Ḥai, Sadeh left for Ereẓ Israel, where he became one of the founders of *Gedud ha-Avodah (the Joseph Trumpeldor Labor Battalion) and was elected its head. As such, he divided his time between working as a skilled laborer (he was an expert stone quarrier) and providing the men of the Gedud ha-Avodah with military training. When the Gedud ha-Avodah disintegrated, Sadeh retired for a while from public service, but presented himself again to the *Haganah at the outbreak of the 1936 riots. He was the first to propose to the Haganah the policy of "breaking out of the perimeter," i.e., not to confine itself to static defense behind the barbed wire fence of the settlement, but to attack the Arab terrorist bands in the open. This policy resulted in the formation of the Haganah field companies (peluggot sadeh, abbr. "Fosh"), which Sadeh commanded until 1938, when they were replaced by the field corps (ḥeil sadeh, abbr. "Ḥish"). Sadeh also became the commander of the new formation and within its framework founded a special commando unit (peluggah li-fe'ullot meyuḥadot, abbr. "Pom"), which incorporated a naval platoon and was trained for fighting on land and at sea. Sadeh commanded the operations of this unit in defending the establishment of the strategically placed new settlement *Ḥanitah in western Galilee. In 1941, when the Palmaḥ was founded – largely on Sadeh's initiative – he became staff officer for Palmaḥ affairs at Haganah headquarters and after a short while was appointed commanding officer of the Palmaḥ, which now had become a countrywide formation. He remained at this post until 1945, when he was promoted to acting chief of the Haganah general staff, and as such coordinated the combined resistance activities of the Haganah and the *Irgun Ẓeva'i Le'ummi and *Loḥamei Ḥerut Israel against the government in the final years of the Mandatory regime.
During the *War of Independence, Sadeh took part in a series of significant operations, the battle for Jerusalem among them. It was he who commanded the successful defense of Mishmar ha-Emek, which turned into a rout of the Arab Liberation Army. Upon his initiative, the Israel army formed its first armored brigade (which eventually became the Eighth Brigade); Sadeh became its commander, with the rank of alluf, and as such took part in "Operation Dani," capturing Lydda Airport and other points of strategic importance in the central sector of the front. One of the brigade battalions played a key role in the capture of the town of Lydda. In October 1948 the brigade was transferred to the Southern Command and in "Operation Yo'av" captured the Egyptian-held police fortress of Iraq-Suwaydān. In "Operation Ḥorev" (December 1948–January 1949) he took Niẓẓanah on the Sinai border and took part in the fighting around Rafi'aḥ (Rafah).
At the end of the war Sadeh retired from the Israel Defense Forces (idf). Throughout his military career he had had a profound influence on the training, tactics, and strategy employed by the Haganah and the idf and was both teacher and commander of most of Israel's senior military officers. Reconnaissance, field engineering, naval, and air operations were all innovations first introduced by him.
Sadeh was also a prolific writer of articles, short stories, and particularly plays, only a part of which were published. In the last years of his life, he worked on his memoirs, of which he completed the part dealing with his childhood and adolescence (Ha-Pinkas Patu'aḥ, 1952). He also wrote Mi-Saviv la-Medurah (1946) and Mah Ḥiddesh ha-Palmaḥ (1950). He was buried at kibbutz Givat Brenner.
N. Lorch, The Edge of the Sword (19628), index; Z. Gil'ad (ed.), Sefer ha-Palmaḥ, 2 vols. (1953), index; Dinur, Haganah, index; M. Braslavsky, Tenu'at ha-Po'alim ha-Ereẓ Yisre'elit, 4 (1962), index; Mifleget ha-Po'alim ha-Me'uḥedet, Le-Zikhro shel Yiẓḥak Sadeh (1952); D. Lazar, Rashim be-Yisrael, 1 (1953), 16–19.