本文聚焦波斯薩珊帝國（Sasanian Empire）的首都泰西封（Ctesiphon），探討波斯政治重心的轉移與脈絡。這座城市自阿達胥爾一世（Ardašīr I, 224-239/240在位）的時代起即是波斯國都，卻並非總是政治重心。本文指出，薩珊政權的政治重心在建國的第一個世紀間曾出現轉移，這個發展與當時西亞的政治、軍事情勢密切相關。自波斯政權建立伊始，以統治者命名的新建城市，是沙普爾一世（Šāpur I, 239/240-270/272在位）等人軍事勝利的象徵，如庫奇斯坦（Khuzestan）的岡地沙普爾城（Gondēšāpur）。羅馬帝國等勢力於3世紀下半葉的入侵，對泰西封造成嚴重威脅，薩珊政權的政治重心隨之東移至岡地沙普爾。不過在4世紀之後，波斯對羅馬與中亞部族頻繁地征伐，沙普爾二世（Šāpur II, 309-379在位）強化西境防禦，泰西封再次成為薩珊政權的政治重心所在。

This article examines the development of the Sasanids’ political nucleus in the third and fourth centuries, focusing on Ctesiphon, the capital of the Sasanids from the very beginning of their regime, as well as certain important provincial cities. While the importance of Ctesiphon and its surrounding areas cannot be overemphasized, a combination of factors drove two transitions. The Sasanian dynasty reached its zenith soon after it was established in 224 C.E.; however, the changing political circumstances in the Near East, coupled with internal chaos in the following decades, made it difficult for the Great Kings to defend their heartland in lower Mesopotamia. Based on a close reading of texts from several literary traditions, the present article argues that during the latter half of the third century C.E. the Persians’ political nucleus made an eastward transition from Babylonia to Khuzestan. While Ctesiphon remained the capital, little information about it from this period is extant. In contrast, the important role played by Gondēšāpur, a newly built city at the center of the Sasanids’ politics for decades, is underscored not only by the establishment of the royal residence but also by the presence of the shah and his court. However, in the fourth century, there was a westward transition and the revival of Ctesiphon. In short, the frontier region had been stabilized and Šāpur II (309-379) needed to launch intensive campaigns on multiple fronts, laying the foundation for this city to again be the center of the Sasanids’ politics for the ensuing centuries.