Why had their men proved powerless to defend them?

Animal Control (in fact, the entire federal government) proves powerless against it.

The picture of the prettiest girl that ever lived will in the long run prove powerless to maintain the sales of bad cigarette.

Syria, which was deeply concerned about the flow of events in Lebanon, also proved powerless to enforce calm through diplomatic means.

But only I have seen a Q prove powerless against you.

But they have proven powerless to reverse the action, ordered by leaders of the judiciary, Teheran-based diplomats and political analysts say.

President Assad, an opponent of both measures, proved powerless to avert them.

But he proved eventually powerless, and Congress sent him an act of war effective on April 21.

Why was it that our truth proved powerless, but lies were effective?

In the end, the wisdom of the East proved powerless against industrial-age neurosis.