Operation Cast Thy Bread was a top-secret biological warfare operation conducted by the Haganah and later the Israel Defense Forces that began in April 1948, during the 1948 Palestine war. The Haganah used typhoid bacteria to contaminate drinking water wells in violation of the 1925 Geneva Protocol. Its objective was to frighten and prevent Palestinian Arabs from returning to their captured villages and to make conditions difficult for Arab armies attempting to retake territories. The operation resulted in severe illness among local Palestinian citizens. In the final months of the war, the government of Israel gave orders to expand the biological warfare campaign into neighboring Arab states such as Egypt, Lebanon, and Syria, but they were not carried out. Israeli prime minister David Ben-Gurion and IDF chief of general staff Yigael Yadin oversaw and approved the use of biological warfare.

https://en.natopedia.org/wiki/Operation_Cast_Thy_Bread