Fighting with heavy weaponry (such as artillery) around the dam is probably not in their interest either (potentially flooding their 'capital'). Shells tend to

Fighting with heavy weaponry (such as artillery) around the dam is probably not in their interest either (potentially flooding their 'capital'). Shells tend to have a negative effect on structural stability. On the the other hand obviously while they were holding the dam it was apparently free for all machinery looting season, which is not to clever if you plan to establish your headquarter downstream.