While no one will argue the importance of gaining and maintaining Situation Awareness (SA), there are a variety of perspectives on the best way to train it. Theoretical work on SA basically claims that we are either aware of the data, or we generate inferences and make these the basis of our awareness. In contrast, sensemaking is the attempt to understand how people arrive at an understanding of events. It covers the strategies people use and the reasons that they may struggle or become confused. In essence, we assert that sensemaking is the process through which SA is achieved. Building on decision making research, we hypothesized that a leader's SA skills can be improved by identifying and building his/her sensemaking skills. To test this hypothesis, a Web-based simulated decision environment in which participants performed an ambush mission while being mentored by a skilled tactician was used. This study measured the ability of students to improve their perception of the elements within a battlefield environment, to combine those elements to develop a coherent understanding of the situation, to use that understanding to mentally simulate possible changes in the situation, and to take appropriate actions to prevent and/or support those future events. With the objective to enhance SA, we structured the main components of the training intervention--the scenarios and the mentoring--to focus on sensemaking rather than tactical decision making. Likewise, the metrics designed to measure SA were also structured around student actions that were indicative of good or poor SA. The scenarios were found to be highly effective in building the students' skills in sensemaking and thereby, improving their SA. By the end of the training, the students demonstrated more complex mental models and a better ability to maintain SA in ambush situations.