In modern military operations, people from diverging backgrounds often have to work together in ad hoc teams. These team members are often well trained to perform their own part of the teamwork. However, for optimal performance they should also act as a team. The question is how optimal team performance can be realized swiftly. In this study we investigated the effect of a brief team strategy discussion. We hypothesized that a brief team strategy discussion in an ad hoc team at the start of a mission has a significant positive effect on the development of a shared mental model, on team processes, and with that on team performance. In an experimental setting, 46 four-person military ad hoc teams were presented with the distributed dynamic decision-making task. We gave half of the teams an instruction to develop a team strategy in 10 minutes, whereas the other half received no such instruction. Teams were randomly assigned to the two conditions. The results supported our hypotheses. A further exploration of the data showed that the teams in the team strategy condition showed more initiative and leadership. Finally, we concluded that accuracy gained more from the team strategy discussion than speed of operations. The results have important implications for military training and practice.