"At one stroke the country lost two outstanding leaders."── quoted from
http://www.ldoceonline.com/dictionary/stroke_1 Definition#5
With a stroke of a pen too?
I doubt it. But it could be. Maybe someone signed an execution command? But probably it refers to a single action.
Think of a stroke as one single action, at one point in time, usually done with the hands or arms. We have strokes in golf, we strike at a baseball with a bat or a fly with a flyswatter. If you had a mighty sword you might fell a tree or cut off a guy's head with one stroke.
Back to the first example, you cancel budget items by writing a line through them. With a single stroke of a pen.
We have other words to describe individual acts of jumping/leaping/bounding. We don't call them "strokes."