[.983 Bug?] perceived value for declaring war

Lord Markin was slowly crushing Magnar, he took him from 4 cities down to 1.  Lord Markin's power rating is 200, Magnar's is 20.  In the diplomacy screen with Markin, the value of declaring war was 980.  So I took it in trade for all his technology and was able to instantly learn 3 new research skills in the tree. 

Seems like an exploit if he is crushing Magnar without my help.