While the rise of armed struggle as a component of political mobilization has been explored in scholarly literature on the mid-20th century Eastern Mediterranean, particularly for the Palestinian case (Sayigh, 1997), the relationship between popular political mobilization and state violence, repression, surveillance, and incarceration has been comparatively neglected. This paper foregrounds this understudied relationship, interrogating Arab Nationalist and Marxist political activists’ encounters with the rising security state in 1950s and 1960s Lebanon, Jordan, Palestine, and Syria. As the social biographies that anchor this paper showcase, members of the Arab Nationalists’ Movement (ANM), the Ba’ath Party, and the Communist Party were routinely surveilled, detained, interrogated, and tortured by state authorities across the Eastern Mediterranean in the post-Mandate period. The timing and degree of monitoring and repression depended on intersecting factors such as activists’ nationalities, specific party affiliations, and personal connections: for example, Palestinian political organizers in Lebanon’s refugee camps described being subjected to harsh surveillance measures in the decade following the 1958 Lebanese Crisis (Traboulsi, 2012) despite political groups’ foresighted attempts to keep the camps out of that conflict, while the Jordanian authorities’ post-1957 crackdown on the Jordanian National Movement coalition of the ANM, the Ba’ath, and the Communists (Anderson, 2005) meted out particularly harsh prison sentences to avowed or suspected Communist activists regardless of their comparatively smaller numbers. However, security state practices of surveillance and incarceration operated within a local and global laboratory, with different states’ intelligence apparatuses learning techniques of espionage, interrogation, and torture from each other as well as from regional and global powers. Hence, while localized factors shaped activists’ experiences of state violence to a significant degree, the broader patterns of surveillance, confinement, interrogation, and brutality emerge consistently through the written and oral testimonies of Arab Nationalist and Marxist political activists. Indeed, this paper draws on oral histories, memoirs, and political party documents to argue that violent and coercive encounters with the post-independence security state formed such an integral part of the experience of popular political organizing that they shaped political parties’ mobilizing strategies, relationships with contemporary political movements, and practices of recruitment, training, and discipline of members.