The Reds decimated (classic definition) their own ranks during the Civil War for units that lost a battle or that retreated. I can’t stand when that word is used to mean “destroyed.” It shows the lack of education that infuses our society due to several generations of federal and union control of the public schools. It also shows the uselessness of English dictionaries since the Webster’s 2nd International.
I must confess, that for many years I myself thought it meant to move one decimal point to the right, i.e., reduce TO 10% (90% attrition) rather than to reduce BY 10%.
I suppose it was because of the way I heard the word used through the years... carelessly. Which, goes to prove your point.
Well anyway, I take consolation in the fact that I always get the usage of effect and affect right, LOL.