walking fire

noun2

1. •
   A line of infantry equipped with automatic weapons advancing in a coordinated attack.

   • To counter this the French introduced 'walking fire'. The infantry used man-carried automatic weapons to keep the defender pinned down with a continuous hail of bullets for those last dangerous yards. — 1975
2. •
   (no longer used) Will o' the wisp

   • Had we no walking fire, Nor saucer-ey'd devil of these woods That led us ? — 1646