The Simian Army is a suite of tools developed by Netflix to improve the reliability and resilience of its cloud-based services. It is designed to simulate various types of failures in a controlled environment, allowing engineers to identify weaknesses in their systems before they lead to real outages. One of the most well-known components of the Simian Army is the Chaos Monkey, which randomly terminates instances of applications running in the cloud. This helps teams ensure that their services can withstand unexpected disruptions and recover quickly, ultimately enhancing the overall user experience.