"But so far I am put on my guard by possible results."

This was enough to put the girl on her guard.

If he did it would only put them on their guard and make things much more difficult.

I only want to put you on your guard, that's all.

"And if he was up to something we'd put him on his guard."

He said nothing, but it put him on his guard.

Not even your entry of the city put them on their guard.

There was no point in putting him on his guard.

They may not know, and any action we'd take now would put them on their guard.

I should like to put the citizens on their guard here.