backfire (forest fire defense)
A controlled fire set ahead of a wildfire to remove fuel and stop its spread. Technical term used in forestry and firefighting contexts.
山火事を食い止めるために向かい火を焚く。
They set a backfire to stop the forest fire.
Compound of 向かい (mukai, 'facing, opposite') + 火 (hi, 'fire'), literally 'facing fire'. The term refers to a fire set to face an oncoming wildfire.