No...you don't have to beat a gym leader to get the HM strength.Go to the safari zone,get HM surf,and find the warden's teeth.Then give it to the warden.When he can talk, he will give you the HM strength. That all
defog is the third usable hm after you beat fantina, the hearthome gym leader.
After you beat the Gym Leader, Steven gives it to you.
After you beat Byron, the sixth gym leader in canalave city.
In Cianwood City, after you beat the Gym Leader, speak to the woman standing just outside the gym, she will tell you that the Gym leader is her husband and all that and then she will give you the HM Fly.
First if you mean strength you must beat the gym leader in pastoria city and she will give the HM strength. Then you teach to a Pokemon and you can use it. If you mean stealth rock you can teach it to a Pokemon if you have the TM for it or sometimes your Pokemon will learn it. I hope this is helpful
You can get the HM Strength after you beat the 7th Gym Leader, Byron. He will give you the HM immediately after defeating him.
you have to get the hm strength then beat the gym leader in canalave city
i am pretty sure it's strength.
beat the forth gym leader
You have to beat the gym leader in Canalave City. you get the hm in the lost tower on the way to Soclan town.
you beat the gym leader.
you first you beat a gym leader then you get the hm strength and teach it to a Pokemon then you push some boulders
defog is the third usable hm after you beat fantina, the hearthome gym leader.
go to olivine..find a tavern near the pokemon center..a sailor will give you STRENGTH HM
The scound HM is Rock Smash you can get it after defeating the gym leader at Rustboro.but then you have to beat mauwile gym leader .then you talk to the person on the right side of the gym.
you need to beat a gym leader .
Beat the Cianwood Gym leader, Chuck. Then a woman will apper when you leave the gym and give you the HM.