According to Pete Townshend in 1968:
When did you start smashing guitars?
“It happened by complete accident the first time. We were just kicking around in a club which we played every Tuesday and I was playing the guitar and it hit the ceiling. It broke and it kind of shocked me ’cause I wasn’t ready for it to go. I didn’t particularly want it to go but it went.
And I was expecting an incredible thing, it being so precious to me, and I was expecting everybody to go, “Wow he’s broken his guitar,” but nobody did anything which made me kind of angry in a way, and determined to get this precious event noticed by the audience. I proceeded to make a big thing of breaking the guitar. I pounced all over the stage with it and I threw the bits on the stage and I picked up my spare guitar and carried on as though I really meant to do it.”
Were you happy about it?
Deep inside I was very unhappy because the thing had got broken. It got around and the
Soon after, Keith Moon joined in by kicking his drum kit off its riser.
A few years later, Jimi Hendrix did Pete one better,, by dousing his guitar with lighter fluid, dropping a match, and THEN bashing it to smithereens.
In case you are interested here is a list of some of the guitars he destroyed and where: