I came to wonder this when some poster basically said that we have Karl Marx to thank for things like better working conditions and the 40 hour work week. I've never heard of Karl Marx in such a role but I've never really studied the matter in-depth.

Is there any truth to such a statement? Did Marx himself or his theories have a significant impact on the development of unions, their tactics/strategy and/or their successes, if so, how significant? I'm especially interested in Germany and Sweden if you have to narrow it down.