Yaacov Pat was a member of Hashomer, a Jewish defense organization formed in Ottoman Palestine in 1909. Together with Yitzhak Ben-Zvi, later President of Israel, she served in the first Hebrew regiments in World War I.^[1] In 1931, Yaacov Pat was sent to Jerusalem by David Ben-Gurion to rebuild the local branch of the Haganah, a Jewish militia.^[2] Pat was in charge recruiting men whereas Rachel Yanait Ben-Zvi was responsible for the enlistment of women.^[3]

Pat's efforts to recruit and train new manpower succeeded, but no funding was available for weapons. Rose Vitales, who worked for the Va'ad HaKehilla Community Council of Jerusalem, convinced Pat that she could organize a fundraising campaign. Soliciting from a screened list of donors, the drive increased the income of the organization from 40 Palestine pounds a month (approximately $160) to 1,000 Palestine pounds per month. This money was put to good use purchasing arms for defending Jerusalem during the 1936 Arab revolt.^[2]

With the help of Rose Vitales, Pat also pushed for the establishment of a branch of Magen David Adom in Jerusalem, which existed at the time only in Haifa. By 1936 that branch was functioning.^[2]

The Pat neighborhood in Jerusalem is named for Yaacov Pat.