I have been to some gyms that have 2, 3, or even 7 or 8 Pokemons defending the gym.
Say, even if there are 2 Pokemons, and one is CP 1700, and the other is CP 2000. My Pokemon is only CP 2200, so it is very difficult to beat them both, because they combine to have a CP of 3700.
If I lose to the second Pokemon and restart the fight, I have to start with Pokemon #1 again... so even if I defeated Pokemon #1, I have to fight both Pokemons again.
And in some situation, I see 3 or even 7 or 8 Pokemons. In this case how can I defeat them all and occupy the gym?