A massive Idaho wildfire forced hundreds of people from their homes on Sunday as high winds pushed the blaze to within miles of two communities.

Managers of the 260,000-acre Mustang Complex fire, ignited by lightning in July in mountainous pine forests dissected by steep, narrow canyons in the Salmon-Challis National Forest, prepared to defend threatened houses along a strategic stretch of highway near the two towns in east-central Idaho.

Fire trucks from a number of Idaho cities took up positions near the tiny towns of North Fork and Gibbonsville, which sit within a 21-mile stretch of U.S. Highway 93, near the Montana border.

“It’s going to test us,” fire information officer Bill Swartley said of the wildfire. “We will defend homes. But if it becomes a safety hazard to fire personnel, we will step aside and let the fire pass.”