Jugurthine War
The Jugurthine War started due to "Roman exasperation with the ambitions of Jugurtha", who had killed his half-brothers, massacred Italians in his civil war against them, and bribed many prominent Romans to support him in the Senate. After the start of hostilities, the first army sent to Numidia was apparently bribed to withdraw and the second army was defeated and forced to march under the yoke. These debacles eroded trust in the ability of the aristocracy to adequately manage foreign affairs.