Today's missions are more complex and more dynamic, requiring significantly increased capabilities and efforts. Governments aim to modernize command and control systems to address these operational needs. Also, maintaining of these huge systems are challenging, obsolescence problem makes modernization inevitable. On the other hand, managing legacy systems and their upgrades are difficult. This paper investigates the difficulties of the legacy system modernization on command and control domain. We performed Systematic Literature Review (SLR) to extract system modernization challenges from the literature.

The unprecedented scale of ultra large scale (ULS) systems spans into various dimensions like lines of code, amount of information processed, number of interdependent hardware and computational components, number of people involved etc. The characteristics of ULS systems due to their scale pose different challenges which could only be addressed by a multi‐disciplinary research rather than the traditional software engineering approaches. In this paper, we focused on proposing solutions against challenges in implementing the future interoperable joint Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) systems. For this purpose, we examined the main research topics to address the challenges in ULS systems. We discussed two main capabilities to enable the vision of future interoperable joint C4ISR. One of these capabilities is the effective and secure use of information across components of the system, while the other one is real‐time fusion of the available information with the local context.