The Marian Reforms were a set of the reforms introduced to the Roman army in the late 2nd century BCE by Roman general and politician Gaius Marius (157-86 BCE). Through these reforms, the Roman army was transformed from a semi-professional militia to a professional fighting force. The maniple system of the earlier Polybian legion was abolished and replaced with the cohort. The property qualifications for military service had also been severed. According to historian Adrian Goldsworthy in his book In the Name of Rome, by the end of the 1st century BCE, Roman politics, society, and the army had profoundly changed. "Marius' career, and the disorder of his times, was a symptom of these changes" (128).
This is a companion discussion topic for the original content at https://www.worldhistory.org/article/1598/marian-reforms/.