This paper discusses the practical aspects of architecting a Semi-Automated Forces (SAF) system for a cloud computing environment and describes some of our recent experiments with SAF technology in the context of a cloud-enabled environment. The rapid transitioning of traditional computer applications such as email to cloud computing is beginning to extend to military simulation. The ubiquity of the global Internet and advances in mobile computing are allowing the military to reexamine its business model for constructive simulation. Distributing exercises has been common for over a decade; however, the model has been based on scheduled, dedicated and often temporary infrastructure. Cloud solutions offer the potential of "anytime, anywhere," on-demand simulation and training capabilities. The primary challenge has been in architecting simulations for virtualization and providing the requisite security for military operations. Solutions to these problems are being vigorously addressed. This paper explores some potential implementations of a Cloud Simulation Infrastructure (CSI) concept - how a simulations system could be hosted and accessed via the cloud. Although not the same as cloud computing, high performance computing (HPC) has some useful similarities to cloud computing and may offer an alternative delivery infrastructure for simulation services. We offer results from our work in HPC and SAF systems as a partial contribution to understanding and defining the CSI concept. In addition, we present results from our work with a web-based interface for managing and deploying SAF resources. Combining the results of these two bodies of work, the HPC and the web-based interface, we have developed prototypical model of SAF computing in the cloud. From this vantage point, we also examine the benefits of the CSI concept, such as ubiquitous access, common (across Services) content, technical and operational standards for training, and potential for tactical mission planning.