had been buttressing

• past perfect progressive

  past perfect progressive

  Used to describe an action that was ongoing continuously in the past up until another past event interrupted it.

  of buttress.
  buttress

  noun

  any external prop or support built to steady a structure by opposing its outward thrusts, especially a projecting support built into or against the outside of a masonry wall.

Related Words

• reinforce
• strengthen
• uphold