How might nationalism and militarism jeopardize world peace?

Raises tensions.

Explanation:

Nationalism is excessive patriotism. Loving your country too much. Militarism is the need for a larger military. Militarism is the feeling that your military needs to be the biggest and baddest. Loving your country in excess and having a massive, powerful military is dangerous. That's what happned to Germany before WW1 and 2.