CBO projects that the costs of implementing the Department of Defense’s (DoD’s) 2020 plans will increase over the next 15 years. CBO also projects that the federal deficit, already at historically high levels, will continue to rise. If rising deficits limit the growth of defense budgets, DoD’s spending may be lower than expected. If the costs of personnel and of operation and maintenance continue to rise as they have in past years, funding for developing and purchasing weapons could experience even larger reductions.