What an elaborate plan to throw me off my guard!

If so, you certainly have taken us off our guard.

But what a wonderful way to put everyone off their guard!

It had waited, or seemed to, until they were certain of success and off their guard.

He was just trying to put poor Bilbo off his guard.

But even he, for that instant, was off his guard.

So he had not been taken utterly off his guard.

Let him think all's well, and he'll be off his guard.

Both were off their guard, perhaps, feeling as though the worst was behind them.

The apparent welcome was only to throw me off my guard.