Instruct: Classify Amazon reviews into positive or negative sentiment
Query: antiquity is not barbarian invasions

Delbruk took a critical look at accepted accounts of battles, did some back-of-the-envelope calculations, and showed how most of these accounts were simply implausible. This is an eye-opening read. However, readers are assumed to already be familiar with most of the battles covered. So, a second source giving those implausible accounts should be kept handy.