Objective: On January 6, 2021, a group of individuals violently breached the U.S. Capitol to prevent congressional action. This introduction to the special issue applies basic theories and principles of group psychology to the insurrection and related events. Our goal is to contribute to an understanding of such events and offer some theoretically guided strategies for resolving and preventing similar group-motivated hostilities. Method: The insurrection and surrounding events that are analyzed throughout this special issue are described. Each article featured in the special issue is previewed, highlighting the theoretical constructs and principles employed. They include dynamic social impact theory, person-situation interactionism, emergent norm theory, focus theory, communication models, intergroup dialog theory, models of crowd behavior, and motivational systems. Finally, we preview the concluding article to the special issue that offers additional perspectives and prospects for the future. Results: Group dynamics offers numerous perspectives that help explain the insurrection and related events. These perspectives also provide insights into how such events can be prevented, and how the social tensions that follow such events can be alleviated. Conclusions: It is critical to develop a valid understanding of the factors that precipitated the attack on the U.S. Capitol. Research on the psychology of group dynamics provides numerous empirically supported theories and principles that can contribute to that understanding. Ultimately, a multiple perspective approach will maximize our understanding of the human tendencies and social institutions that promote and dissuade group-based violent extremism, such as the January 6, 2021, U.S. insurrection.