I wasn't feeling too challenged by challenging, so I started a hard game.  Between turns 70-100 Yithril and his two cities went from 50 power to 500.  I found out how a short while later when 14 juggernauts crashed my border.  So I figure he was using the free rush bug, no biggie.  Decided to see how long I could last  - put some watch towers on roads to break them up, started training mounted units for movement.  I figured I'd keep his stacks busy taking and retaking cities while I built up some mounted ranged troops to pincushion slow juggs.  Instead, each city he took got razed immediately.  Is that typical?  When I take a city on challenging it forces me to wait 5 turns before I am allowed to raze it.