Bayern paid Dortmund 37 million euros for Germany star Mario Goetze last season and Poland striker Robert Lewandowski is set to follow in May.
Dortmund won consecutive Bundesliga titles in 2010-11 and 2011-12, culminating in Borussia’s 5-2 drubbing of Bayern in the German Cup final in May 2012.
“Bayern wanted to destroy us,” Watzke told German daily Bild with third-placed Dortmund currently 17 points behind leaders Bayern in the table.
“Not in the sense they wanted to break us as people, because they don’t like us, but because they wanted to switch us off permanently as a direct competitor.
“They have helped themselves to our players, so we wouldn’t be a danger to them again.
“It was all done legitimately and we have to live with that.
“When we beat Bayern 5-2 in the German Cup final, I saw it in the faces of Munich’s top figures. Bayern then hit back.
“There is now no other league which is dominated by a single club like the Bundesliga.”