RISK Probabilities

I enjoy playing RISK, but I haven't in a while.  The other day I came across JRISK and started up again.  JRISK is cool because it is open source and it took the most boring part of the game out, the defense.  Now with its handy "auto defend" you just have to worry about attacking and strategy, not clicking on the roll button.  

It has been quite a while since I last played, and I had always wondered what the probabilities of the different die rolls were.  Well, one Saturday morning I did a quick calculation and found the probabilities and decided to slap them up on my new web page for everyone to see.  (and critique)  There is also a spreadsheet with the probabilities.

The thing I noticed was the success rate jump if you leave two defenders on a territory versus only one.  If you are defending and leave one army on a territory you only have a  34% chance of surviving.  With two armies on each territory, your chances of creating more attrition goes up.  This is only evident with a Monte Carlo simulation.  Hopefully I can get that code up as well.  In the mean time, I hope these give you a good start.