In 2013, the Ground Combat Exclusion Policy (GCEP) for the United States military was eliminated, and in December 2015 Secretary of Defense Ash Carter opened all ground combat military specialties and positions to women without exceptions. Using primary survey data that I collected in 2021 from the 33 active-duty Army brigade combat teams (BCTs), this dissertation explores the effects of exposure to serving with women on male opinions about gender integration in the combat arms, perceptions of women’s capabilities (physical fitness and mental toughness), and predicted effects of gender integration on unit cohesion and unit performance in the formerly all-male Infantry and Armor branches of the Army. This mixed methods study explores the following question: To what extent does exposure to serving with female soldiers and officers in combat units help explain differences in male support for gender integration, and perceptions about its effects? Since the policy change is fairly new, a natural experiment in military assignments provided an opportunity to learn about how exposure impacts male soldier opinions in formerly all-male units. Women have been assigned in clusters to some Army Infantry and Armor units but not others due to their small numbers. At the time of the survey, there was still significant variation in exposure to serving with women in Infantry and Armor units, so exposure is examined as a treatment variable to determine if male opinions differ by unit level of exposure. The women in these newly integrated units, as well as the men and women in the associated combat support units that have been gender integrated for decades, are also included in the analysis for comparison. The findings demonstrate that the presence of women within a formerly all-male Infantry or Armor platoon or squad, and exposure to a female leader, predict that a male respondent is significantly more likely to support gender integration in the combat arms, perceive that female soldiers in their units are physically fit and mentally tough enough to be effective in their military jobs, and is less likely to worry about gender integration effects on unit cohesion and performance.