To reset/start, press the "r" key, then click the green flag. If you press the r key when the green flag is pushed, the troops will disappear while the simulation loads, then reappear when it is complete. To move troops, click on them so they are "selected", then press an arrow key. Note: dragging troops does not work. Troops die as they cross no-man's land, but only if an enemy troop is manning the machine guns on the trenches nearest that no-man's land. Troops may attack the enemy by the same process that they move--just push the arrow key in the direction of the enemy. The fighting is slightly randomized. Each block starts with 100 troops but the block will display the number of troops it has when you mouse over it. After a fight, the number of troops left is displayed until you mouse over it. A fight may be stopped by clicking on the attacker, but only if the attacker has invested half of their troops into the fight. Multiple blocks can attack a single enemy. Resetting usually works best if the stop button is pushed first. De-select troops that you don't need to have selected because selecting a troops causes the program to run a much longer script, and too many selected troops may create lag. Some tips: push the stop button before resetting, don't move a troop while another troop is crossing no-man's land (simply because it looks weird--there's no effect otherwise). Also, note that when one fight is stopped, any fights going on with that same block will also be stopped.
Credit to Mr. Herzog, my Coding teacher, and Mr. Harms, my history teacher.