The communist May Day has always been big celebrations in communist dominated countries. In countries teetering toward communism (such as ours?) such parades were a source of riot and unrest.
Communists, through their agent "cats paws".. were and are, always stirring up trouble in contiguous free countries.
Back inthe 1960s, when I was serving in West Germany, we troops were advised to play it cool on May Day.
We were told we had best stay on post that day...and if we lived off post..to stay where we lived for that day.
One day I happened to be part of a convoy, travelling alongside the Iron Curtain on May Day..
We were pelted with stones by some of the locals.. Don't ask me to explain, except perhaps some blamed us for their being seperated from loved ones living on the other side of the Iron Curtain.
Of course..in normal circumstances, many, many more thanked us for being there.