By Marta Guttenberg
June 20, 2025

Philadelphia

Day & Zimmermann, a Philadelphia based, family-owned company has been in the business of supporting imperialist wars and interventions for over 100 years. Since Oct. 7, 2023, and the escalation of Israel’s genocidal war in Gaza, activists in Philadelphia have been protesting outside the company’s headquarters on Spring Garden Street.

June 24th will mark the fourth early Tuesday morning protest — starting at 6:30 a.m. — outside their offices in an effort to raise awareness among people in the area about the company’s complicity in supplying weapons to Israel used to kill civilians in Gaza. An average of 30 people have shown up each week to participate in reaching out to area workers and students from the nearby Philadelphia Community College about their murderous neighbor.

History of support for imperialism

The company was founded in 1901 as an engineering firm supplying services to manufacturers. By 1908 it was involved in building the Gatun Lock system for the Panama Canal on land stolen by the U.S. from Colombia. Construction of the canal involved significant exploitation of labor, racial discrimination and a high death toll among workers, especially those from the Caribbean.

In the 1940s, Day & Zimmermann became involved with the construction of munitions plants for the U.S. war efforts, leading to contracts to operate them in later years, a business the company continues to this day.

Harold Yoh Sr. acquired Day & Zimmermann in 1961 and folded in his engineering company Yoh as a company subsidiary. Harold Yoh Jr. took over the family business in 1976. His acquisitions brought the company into naval engineering, nuclear and fossil fuel power plant maintenance and security services for the Los Alamos nuclear laboratory in New Mexico.

In 1998 the next generation led by Harold L. Yoh III took over. The company continues to provide services to the empire, designing and building the 101st Airborne Command and Control headquarters in Fort Campbell, Kentucky, maintaining 70 nuclear power plants around the U.S. and providing security services to military and industrial installations around the world.

But what has made Day & Zimmermann the target of multiple protests in Philadelphia — starting during an International Women’s Day protest in March 2024 — is its role as the supplier of most of the artillery munitions used by the Israel Occupation Forces in Gaza. This includes the highly explosive M830A1 rounds Israeli tanks fired at a United Nations school in Gaza in November 2023.

Israeli tanks fired the M830A1 rounds on Jan. 29, 2024, that killed 6-year-old Hind Rajab, her family members and the medics who attempted to rescue her in the Gaza neighborhood of Tel al-Hawa. The serial number on an exploded round found inside the ambulance indicates it was produced by Mason & Hanger, a subsidiary of Day & Zimmermann. (workers.org/2024/03/77442)

As death tolls from the U.S.-Israeli genocide in Gaza continue to mount, the deaths of over 55,000 Palestinians provide the reasons to continue these protests!