 As VC fire increased in intensity, the soldiers of Company D picked up the distinctive sound of a U.S.-made M-60 machine-gun firing from the southern flank.Allen assumed that Company A was approaching his perimeter, so he ordered them to cease-fire because he feared his rifle companies were firing on each other.However, the order was also passed down along the formation of Company D, which enabled the 271st Regiment to gain fire superiority.