Despite the strength of the U.S. dollar, it was actually the U.S. that fired the first shot in an undeclared currency war whose risks investors need to mitigate through conservative investments, Janus Capital's Bill Gross warned.

Writing in his March investment outlook, the bond manager reached beyond today's headlines about the Swiss franc-euro peg back to the Federal Reserve's near-zero rate reduction immediately following the Great Recession six years ago.

That rate cut effectively devalued the dollar by 15%, a move that Gross said, in a novel explanation "seldom" addressed by other analysts, was the reason the U.S. has led the world in global growth since the financial crisis.