1. Attacking Force

    Enter your starting army:
  2. Defending Forces

    Enter, in order and separated by commas, the sizes of the armies you plan to attack:
  3. Fortifying Units

    Enter the minimum number of units you wish to leave behind at each location (starting location + attacked locations). You may leave this field blank, which defaults to 1 unit left behind at each location.
  4. Calculate

    Push the button to calculate the probability of success!

    Calculate Probability
Source code.