This paper argues that the 70-Day Siege of Sanaa from late November 1967 to early February 1968 turned the tide of the Yemeni civil war, and set the stage for the successive military regimes of contemporary Yemen. On September 26, 1962 a small palace coup in Sanaa, Yemen forced the ruling Zaydi Imam to abandon his capital for a tribal refuge in the far north of the country. The years of fighting that followed split the country into Royalist and Republican sides and, in the process, turned Yemen into the only place in the Arab world where the competing ideologies of Arab nationalism on the one hand and conservative Islamic monarchism on the other were in direct conflict with each other. Egypt, Saudi Arabia, and Britain were all drawn, in various and varying ways, into this confusing conflict, where tribal loyalties clashed with Cold War ideologies. Set against this backdrop, my paper will document how at the conclusion of the war a right-wing faction of the military was able to take control of the Republican side and secure victory. This right-wing faction broke from the more liberal-wing of the Republican defenses during the Siege of Sanaa and defeated not only its internal enemies but also its larger Royalist foes. I will further argue that the right-wing faction that emerged victorious from the siege and the civil war itself laid the groundwork for the series of military regimes that continue to rule Yemen until today.