How did militarism manifest itself

The militarism manifests itself through militarization and military expansion.

Explanation:

The militarism is more often than not highly dangerous, not just for the country that is involved in it but also for the region or even the whole world. Basically, the militarism means that a country is investing heavily into military equipment and development of it, as well as increasing the number of military personnel. The more dangerous aspect of it is that the purpose of this is to expand through attacking neighboring countries or countries that are seen as rivals.

On numerous occasions there has been situations like this, often with catastrophic consequences. One example is Nazi Germany which terrorized Europe. Japan too massacred East and Southeast Asia. The United States and the Soviet Union engaged in this process after the World War too and it pushed the world into the Cold War which almost escalated to a new world war.