Situation Assessment and Decision Making (SA & DM) in mission critical scenarios is a complex cognitive task involving assessment of numerous variables which are often interdependent. Tasks are performed by individuals, teams and organizations and information is provided by different sources. Team members often perform a specific role, but must share information and a common understanding of the problem with other team members to be effective. Proper automated support could alleviate the problems of distributed cognition. This paper defines many requirements for distributed decision support systems, to support mission critical operations such as disaster recovery, personnel evacuation, and medical support during a pandemic. The paper also addresses the difficulty in developing such systems.