What exactly do you mean by "foreign military operation" exactly? I mean, Taft never sent soldiers to foreign countries, but nearly stepped in during a period of strife in Mexico. He did help the Argentinians buy battleships as part of his overall economic policy for South America.

There are probably a few others but I would need to look them up.

William Henry Harrison, although U.S. forces were en route to a punitive expedition to Samoa during his brief presidency.

That's it.