Question

How did nationalism contribute to the french desire to retake the alsace-lorraine region?

Answer 1

A character of nationalism is to conquer and expand empire to include land seen as part of the national heritage. The Alsace-Lorraine region had been disputed land between Germany and France. The area had moved back forth many times cause war between the two nations. France wanting to regain the area was an attempt to reintegrate French people under the French flag. 

Answer 2

The French wanted to remove Germans from the land Germany had taken in the war.