Request Help with a discussion question

"Idealism vs. Realism in International Politics"  Please respond to the following:

Roskin and Berry allude to the tendency toward idealism in international politics before WWII ended in 1945, but the tendency toward realism after that year.

• Explain what the authors mean by “idealism” and “realism” in international politics.
• Characterize the differences between the world before 1945 and the world after that year with respect to international relations.
• Explain the causes of the transition (from idealism to realism).

Again - this is a discusssion question.  No need for a 2 page response.  A couple of paragraphs will do.  As long as you answer the three bullet points, we will be good to go.  No format preference either.  I'm willing to pay $5 for satisfactory completion of a response to the aforementioned question.