Both militarism and mobilization were a major cause for a WWI to become as terrible as it did and that is why they should be included in its description.
Militarism basically means that the government should have a strong army and be able and should deploy it in order to accomplish its goals. Militarism can be seen in countries which strengthen military without any immediate threat to them. Like Nazi Germany which was surrounded by countries that were very peaceful and yet went and worked on creating a powerful army forces.
Mobilization means recruiting and forcing all able citizens to serve in the war and send them to the front. That is they were mobilized for military service. For WWI a large number of people were mobilized. <span />
