The cuts are part of a broader plan to shrink the upper ranks by 10 percent over five years, restoring them to the their size when the country was last at peace, before the attacks of Sept. 11, 2001.

The changes are projected to save only a modest amount of money, but defense officials said they are symbolically important as the Pentagon adjusts to an era of austerity. The Obama administration proposes to squeeze $450 billion from defense budgets over a decade. An additional $500 billion in cuts will be triggered if Congress cannot agree on a deficit-reduction plan in the next year.

Thinning the ranks of generals and admirals is also necessary to make the military more nimble, said Vice Adm. William E. Gortney, director of the Joint Staff at the Pentagon.