SACRAMENTO, Calif. (AP) — Last week, managers overseeing the fight against the massive wildfire scorching California’s Lake Tahoe region thought they could have it contained by the start of this week.

But on Monday the Caldor Fire crested the Sierra Nevada, forcing the unprecedented evacuation of all 22,000 residents of South Lake Tahoe. That drastic move might have been unnecessary if authorities could have thrown more firefighters at the blaze when it was small. They didn’t because at that point the Dixie Fire was raging to the north, on the way to becoming the second-largest wildfire in California history.

Wildfire experts say losing that initial opportunity meant it would be virtually impossible to corral the Caldor Fire.