Contradiction

Thus all collisions in history have their origin, according to our view, in the contradiction between the productive forces and the form of intercourse. But also, to lead to collision in a country, this contradiction need not  necessarily come to a head in this particular country. The competition with industrially more advanced countries, brought about by the expansion of international intercourse, is sufficient to produce a similar contradiction in countries with a backward industry. 

I was able to follow the text up to this point. I'm not quite clear about what contradiction they are talking about.