His great success in war was due largely to his definiteness of aim.

He knew what he wanted to do, and did it.

He was like a great burning glass, concentrating the rays of the sun upon a single spot; he burned a hole wherever he went.
The sun's rays scattered do no execution, but concentrated in a burning glass, they melt solid granite; yes, a diamond, even.

There are plenty of men who have ability enough, the rays of their faculties taken separately are all right; but they are powerless to collect them, to concentrate them upon a single object.

They lack the burning glass of a purpose, to focalize upon one spot the separate rays of their ability.
Versatile men, universal geniuses, are usually weak, because they have no power to concentrate the rays of their ability, to focalize them upon one point, until they burn a hole in whatever they undertake.
This power to bring all of one's scattered forces into one focal point makes all the difference between success and failure.