Hold the presses! The CMOS stands up to the Marines.
Q. About two spaces after a period. As a U.S. Marine, I know that what’s right is right and you are wrong. I declare it once and for all aesthetically more appealing to have two spaces after a period. If you refuse to alter your bullheadedness, I will petition the commandant to allow me to take one Marine detail to conquer your organization and impose my rule. Thou shalt place two spaces after a period. Period. Semper Fidelis.
A. As a U.S. Marine, you’re probably an expert at something, but I’m afraid it’s not this. Status quo.
From Chicago Manual of Style monthly Q&A. [Extra period in Q added by me.]