This study examines the effectiveness of the Force XXI mechanized infantry platoon organization. The study first reviews similar historical mechanized platoon organizations. The purpose of the historical review is to determine the evolution of these organizations and to gain insights as to why they changed. Second, the study assesses the current effectiveness of the Army of Excellence light and mechanized platoons to reveal the potential effectiveness of the Force XXI platoon. Finally, the thesis assesses the effectiveness of the Force XXI platoon by using the historical conclusions drawn from previous organizations combined with the analysis of current platoon effectiveness. The study confirms the hypothesis raised in this thesis. Historical conclusions and demonstrated marginal effectiveness of current organizations, reveal that the Force XXI platoon may not be an effective organization for twenty-first century. Finally, this thesis concludes with a recommendation that is organized to correct the issues and problems raised in this thesis.