Nowadays, time, scope and cost constraints along with knowledge requirements and personnel training constitute blocking restrictions for effective Offensive Cyberspace Operations (OCO). This paper presents RedHerd, an open-source, collaborative and serverless orchestration framework that overcomes these limitations. RedHerd leverages the ‘as a Service’ paradigm in order to seamlessly deploy a ready-to-use infrastructure that can be also adopted for effective simulation and training purposes, by reliably reproducing a real-world cyberspace battlefield in which red and blue teams can challenge each other. We discuss both the design and implementation of the proposed solution, by focusing on its main functionality, as well as by highlighting how it perfectly fits the Open Systems Architecture design pattern, thanks to the adoption of both open standards and wide-spread open-source software components. The paper also presents a complete OCO simulation based on the usage of RedHerd to perform a fictitious attack and fully compromise an imaginary enterprise following the Cyber Kill Chain (CKC) phases.