OK, its a teaser heading. And the "who" is rather easy because of the American flag, but the "where" is more difficult. And, "who" are the military types in white uniforms? And "when" is it?
So let's keep it easy and fill in the blanks.
The "where" is Vladivostok, and the date is August 1918, and the military in white uniforms are a Japanese contingent welcoming the American contingent.
Another view of the march:
The building in the background was the GHQ for the military of all the so-called "Allies" (hence the flags) who took part in the operation. The purpose of the intervention, was ostensibly to protect a Czech force that was attempting to escape defeat by using the Siberian railway to cross Asia to Vladivostok and then by ship back to Europe.