For most of its history, the U.S. military has maintained a policy of exclusion toward lesbian, gay, bisexual, and transgender (LGBT) people serving in uniform. The justifications for these exclusions have included the view that being homosexual or transgender is a psychological disorder, that it undermines military morale and effectiveness, and a fear that LGBT people would be vulnerable to foreign espionage. Explicit policies banning consensual homosexual sex—and excluding from service those who engage in it—date to the period between World Wars I and II, but de facto efforts at exclusion have existed since the early days of the republic. Regulations governing homosexuals in the military came under pressure in the 1970s and 1980s as societal views toward lesbian, gay, and bisexual (LGB) people changed, and those LGB service members discharged under the policy increasingly challenged their treatment in court. (Public pressure to change regulations governing transgender people in the military arose mostly in the 2000s, though litigation efforts date to the 1970s.) In addition to general shifts in public and legal opinion, the debate over LGB people serving in the U.S. military was affected by the experience of foreign militaries that allow LGB people to serve. United States law began to loosen formal restrictions on LBG people serving in uniform with the passage of “Don’t Ask, Don’t Tell” (DADT) in 1994, but it still required LGB people to serve in secret. Changing public perceptions of LGB people and problems implementing the ban galvanized support for eliminating such restrictions. In 2010, President Obama signed legislation repealing DADT and removing all restrictions on LGB people serving in the military. However, transgender people do not enjoy the same rights. The Trump administration has revised Obama-era rules on transgender service members to enable greater exclusion. The issue is being contested in the courts and appears ripe for further political and legal dispute.