Combat begins when two pokemon, either from a trainer, or someone, else decide to fight. There is no surprise round.
1. Roll initiative, both pokemon roll a 1d20, and add 1/2 their speed rounded down to the end number. Whoevers is higher goes first.
2. Declare your attacks and choose what you do, and play normally. When the last pokemon has taken his turn, the round is over.
4. Pokemon roll 1d20 and add 1/5 of their accuracy score rounded down, to determine if they hit another pokemon. They are trying to achieve a number higher than the other pokemons defense, which is 7 + 1/5 their speed rounded down. Meeting it or beating it means they hit. If they are lower, it means they miss. The fastest pokemon gets to attack first.
5. Roll damage and subtract the damage from your hp as normal...
6. Roll new initiative, due to the slow nature of forum play, we can incorporate this dynamic of fighting into the game.
When a pokemon reaches 0 hp they're unconscious briefly, wake up when the fight is over, and are too exhausted to fight. They cannot use any abilities until they wake up, either by resting for a night (and being at 1 hp), or by going to a pokemon center (and being fully healed).