This paper addresses how Arab nationalism—identity and movement based on the shared sentiment of affiliation with the Arab world—was expressed in the Maghrib region. This case study contributes to the poorly explored history of Maghrib-Mashriq relations, by analyzing the migration of approximately 2,700 Tunisian volunteer soldiers who left their country in 1948 to fight in the Arab-Israeli war. Moreover, by revealing the spontaneous and grassroots nature of the movement, the study provides a useful corrective to the dominant narrative of the modern Maghribian history, which is based on the dichotomist opposition between the colonial authorities and the native resistance. The analysis of the paper is based on French archival sources and original Arabic sources—especially Tunisian newspapers. Tunisian involvement in the Palestinian issue under the banner of Arab solidarity resulted in conflict between two different directions of nationalism in Tunisia. On the one hand, the nationalist leader Habib Bourguiba and his party, Néo-Destour, tried to use the Tunisian volunteers to achieve their own goal of pressing the question of the Maghribian independence among fellow Arab countries. On the other hand, young leaders of the Zaytuna mosque in Tunis advocated Arab and Islamic identities of the Tunisian nation, which led to their incitement of boycotting Tunisian Jewish merchants. Thus, in Tunisia, Arab nationalism carried two different meanings: the political understanding of Arab nationalism to counter the European colonial powers, and the religious conception of an Arab nation based on Islam and the shared language. The paper also examines the gap between nationalist leaders and the grassroots volunteers who were ideologically and socioeconomically heterogeneous. The paper reveals that the volunteer movement started spontaneously and, in many ways, independently from the nationalist leaders’ intentions. Although nationalist leaders tried to coopt the movement by mobilizing volunteers selectively, the scale of the volunteer movement went beyond their control. The mobilization of the volunteers without sufficient control ended up allowing the British army to deport the majority of the Tunisian volunteers from Egypt. The paper argues that, besides the colonial authorities, the nationalist leaders’ disregard for the aspirations of the grassroots elements disturbed the Arab nationalist solidarity.