WASHINGTON (AP) — Harold Brown, who as defense secretary in the Carter administration championed cutting-edge fighting technology during a tenure that included the failed rescue of hostages in Iran, has died at age 91.

Brown died Friday, said the Rand Corp., the California-based think tank which Brown served as a trustee for more than 35 years. His sister, Leila Brennet, said he died at his home in Rancho Santa Fe, California.

Brown was a nuclear physicist who led the Pentagon to modernize its defense systems with weapons that included precision-guided cruise missiles, stealth aircraft, advanc...