假道伐虢
Stratagems of Contending · 混战计Request passage through a weaker state to attack a third party — then use the opportunity to conquer the state you passed through.
The state of Jin requested permission to pass through Yu to attack Guo. After Yu agreed, Jin conquered Guo on the way, then turned back and conquered the defenseless Yu as well — having used them twice.
Microsoft bundled Internet Explorer with Windows — asking users for "passage" through their operating system. Once inside, IE displaced Netscape (the "Guo"), and the operating system dominance was further cemented (the "Yu").
App stores often provide free tools and APIs (passage) to attract developers. Once developers build on the platform, the platform owner changes terms, adds fees, or competes directly — having used the developers to conquer the market.