Linked from
The 16 pages that link to Battle of al-Qadisiyyah, each with the reason it gives.
KufaRelated: The conquest of Sasanian Iraq preceded the establishment of Kufa as a garrison town.
Khosrow IIRelated: The empire weakened after Khosrow's reign and later fell to Arab-Muslim armies.
CtesiphonRelated: The defeat helped open the route to Ctesiphon and the Sasanian heartland.
Yazdegerd IIIRelated: Its defeat opened the route toward the Sasanian capital.