What strong forces caused friction between the countries of Europe in the years leading up to 1914

Military alliances between the nation sin Europe caused invariable tensions int he countries.

Explanation:

The time of the late 19th and early 20th century was one of great prosperity for the European nations as they were gaining enormous wealth from their colonies and the trade was booming too in the country so they were skeptical of each other's influence.

This resulted in a station where all countries had some military alliances to protect themselves form a rival country and this made them cluster in to overlapping and confusing groups of loyalties marking the tensions even more high than they were.