WASHINGTON (AP) — President Barack Obama's selection of a former top Pentagon lawyer to head the Homeland Security Department suggests the agency will be stepping back from its preoccupation with immigration to focus more on protecting the nation from attack.

Jeh Johnson, if confirmed by the Senate, would replace Janet Napolitano, who left the DHS to become president of the University of California system. Obama is expected to announce Johnson's nomination today.

Unlike Napolitano, who was governor of Arizona, Johnson has spent most of his career dealing with national security issues as a military lawyer. Issues he handled included ending the military's don't-ask-don't-tell policy for gay service members and changing military commissions to try terrorism suspects rather than using civilian courts.