break
Often people use breach to indicate a break in protocol or security. For example, in many movies where a character, like Jason Bourne, breaks into a secure a facility, like the FBI, it is considered a security breach. His entrance into the secure facility breaks the "bubble" of security around the data or facility. The circle option doesn't work at all. A promise is a pledge to do something. It should not be broken. A union happens when two things come together. This is not the case.