"Deadly Earnest" Quote to Abraham Lincoln

I am trying to locate a specific quote that I think I read in Catton, long ago. I believe it was by Daniel Sickles to Abraham Lincoln, and it went something like this: "We have many skilled generals, but you need men who are in deadly earnest." I'm sure the wording is wrong, and I do not have the resources to search for the correct wording.

Thanks for any help.

I've tried researching your question. I know I've read it before, and I think you're right about the Catton attribution. I have all of Catton's books, but most are not close at hand. I'll keep at it and update when I have anything new to offer.