It was founded in late 1947 as the Field Corps unit responsible for the defence of Jerusalem and its surroundings, where it operated during the 1948 Arab–Israeli War along with the Harel Brigade.

[2] The Jerusalem region, and hence the brigade's theatre of operations, stretched from the Dead Sea in the east, Atarot in the north, Gush Etzion in the south and Hartuv in the west.

[4] Yisrael Amir, who had held several staff positions before the war, was appointed to command the brigade on the recommendation Moshe Sneh.

[5] Before the Haganah reorganised its infantry forces in February 1948, the brigade was divided into two battalions; the first was responsible for northern Jerusalem, Motza, Atarot and Neve Ya'akov, and was commanded by Zalman Mart.

[4] David Shaltiel, who replaced Amir as a brigade commander in the same month, reorganized the forces and divided Jerusalem into five regions, four of them going to the Guard Corps, with the Old City and southern neighbourhoods going to the operational battalions (61st and 63rd).

[6] Shaltiel's method of command worsened the discipline issues until in June 1948 the 61st Battalion rebelled and was subordinated to the Harel Brigade until August 1948.

[4] In May 1948, Yisrael Galili created a staff unit in Etzioni that was based in Tel Aviv, responsible for the Jerusalem region's outlying and isolated settlements.

[10] Moshe Dayan replaced David Shaltiel as the regional commander of Jerusalem on July 25, 1948,[11] although he failed to affect significant territorial changes in the area.

[20][21] During the Battles of the Ten Days, Etzioni was set to significantly expand Jewish control of Jerusalem and its surroundings, including capturing the Old City.

[22] Etzioni's 62nd Battalion participated in Operation Kedem on July 16–17, to take over the Old City in a frontal assault, due to a lack of time imposed by the impending ceasefire, but failed to breach its walls.

[23] After the second truce of the war, Etzioni participated in Operation Yekev, meant to capture the mountains of Beit Jala, but failed in its mission and retreated.