It would be impossible to overstate the impact of Pentagon spending on California's evolution during and after World War II.

The state was a major manufacturer of ships, airplanes and other military implements during the war, as well as a training and staging area for the Pacific Theater, and hundreds of thousands of men and women migrated to the state for war-related jobs.

California might have returned to its prewar status as a bucolic and largely rural outpost on the left coast of the continent had the Cold War not followed, thus maintaining the many military bases opened during the war and more importantly, from a socioeconomic standpoint, fueling a defense industry that provided hundreds of thousands of high-paying jobs.

Eventually, direct and indirect spending on defense, including research contracts that supported California's universities, evolved into the state's largest single industry, supercharging a half-century of human and economic expansion. The Pentagon funneled fully a fifth of its money into California and military-related spending had secondary and tertiary impacts that are almost incalculable, such as fostering the development of the high-tech industry, and making California a magnet for immigrants from other nations.

The peak of both the Cold War and California's defense industry came in the 1980s, during the much-vaunted military buildup pushed by President (and former California Gov.) Ronald Reagan, but when the Soviet Union blinked at the prospect of a more intense arms race, defense spending quickly declined and California plummeted into the worst recession in a half-century. A 1994 state legislative report said that in the preceding seven years, California had lost 200,000 jobs in private defense industries and an additional 25,000 from base closures.

The latter -- the shutdown of dozens of bases ranging from McClellan Air Force Base in Sacramento to the Long Beach Naval Shipyard and Monterey's Fort Ord -- received most of the political and media attention, but economically, the losses of private defense contractor jobs were much more devastating.

Just as a half-century of heavy military spending in California massively altered the state's social, economic and physical landscapes, so did its rapid decline. At least a million Californians packed up and left California during the early 1990s, seeking jobs in other states whose economies were expanding, and it's clear that many, if not most, were displaced aerospace workers and their families. Cities such as Long Beach that had been heavily dependent on defense jobs underwent wrenching change; in Long Beach, recent immigrants from Asia and Latin America occupied houses vacated by the departed defense workers and quickly and radically changed the cultural and political milieu of the city. It evolved from electing conservative Republicans such as George Deukmejian and Dan Lungren to favoring liberal Democrats such as Alan Lowenthal and Betty Karnette.

This brief history -- it would take a book to do the subject real justice -- is offered because California's defense industry may be facing a new evolutionary cycle.

The Bush administration's more expansionist aerospace policies are beginning to be felt in California's defense industries -- and if its Mars exploration program becomes reality, California could be in line for much of the research and development work.

But at the same time, Defense Secretary Donald Rumsfeld wants the commission that handles military base closures to take another whack, seeking to shutter perhaps a fourth of the nation's 425 installations. And that makes California politicians nervous.

Gov. Arnold Schwarzenegger vowed in his State of the State address to spearhead efforts to protect California installations from the base closure commission, local boosters are raising money for Washington lobbying efforts and publicity campaigns about the bases' assets are being cranked up.

We can expect to hear much political drumbeating about the threat closure in the months ahead; a state legislative committee is already planning hearings. But we should keep it in perspective, because California's economy is no longer tied to the Pentagon, and the jobs involved in the bases believed to be vulnerable are a tiny fraction of California's work force.