While serving in the military in 1955–56, Adonis was imprisoned for his membership in the Syrian Social Nationalist Party (following the assassination of Adnan al-Malki), Led by Antoun Saadeh, the SSNP had opposed European colonization of Greater Syria and its partition into smaller nations. The party advocated a secular, national (not strictly Arab) approach toward transforming Greater Syria into a progressive society governed by consensus and providing equal rights to all, regardless of ethnicity or sect.