6971
This was a major engagement of the American Civil War , and between December 31 and January 2 , 1863 , the rival armies suffered a combined total of 23,515 casualties .
 event: American Civil War
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 event: American Civil War