In May 2014 the Government of Sweden, represented by the Ministry of Defence of Sweden, and the Ministry of Defence of Finland signed an action plan for deepened defence cooperation. The two defence forces were tasked to look at opportunities resulting from the cooperation. The discussions between the navies resulted in a vision and road map for establishing a Swedish-Finnish Naval Task Group (SFNTG) and in order to explore the vision and the road map a table-top discussion (TTD) was held in November 2014. The TTD was set up as a Concept Development Assessment Game (CDAG) although the method was adapted to suit the aims of the TTD. In short the adapted version was set up to give perspectives from two cooperating teams rather than having two opposing teams as in a traditional war game. Furthermore, the confrontation and challenge phase was changed into a more open discussion and the documentation phase was simplified. The TTD did successfully investigate the utility and feasibility of the vision of the SFNTG and identified challenge areas using the adapted version of CDAG as method. As SFNTG was a premature concept before the TTD we show that this method also is suitable for development of concepts in early phases.