Here is how to get HM Strength in Pokemon Red:
you get hm strength and hm defog after defeating two gym leader.Fantina(defog) Byron(strength).
To get the HM Strength in Pokemon Red you need to do a little side quest. This quest involves finding the Safari Zone Warden's missing Gold Teeth which can be found in Area 3 of the Safari Zone itself. After finding the Gold Teeth and bringing them back to the warden he will give you the HM for Strength.
let all you're Pokemon faint and you'll return to the last Pokemon center you used.
You can get the HM Strength at Nimbasa City. One of the buildings behind the Poke Center will have a man with blue hair and will talk to you about the HM Strength and will give you it.
If you have beaten Mauville Gym and have gotten HM ROCK SMASH, go to RUSTURF TUNNEL and clear out the rocks. The digger will grant you HM STRENGTH.
there is no rock smash in Pokemon Red. there are only 5 HM's in Red version. the rock smash was introduced in the Silver and Gold versions.
From a man in the building north west of the Pokemon Center in Nimbasa City.
Strength and Surf.
In Olivine City, go to the Pokemon Center. Don't go in. Then, if you're there, go left, to the building next on the left. In there, are men.talk to the man sitting at the table. He will give you the Strength HM
HM STRENGTH HM STRENGTH
The way you get waterfall is by trading the waterfall HM from Fire Red Version or the other Version that have waterfall HM ( you can trade with a link cable or wireless adaptor)
HM 4