An example of a tombstone squeeze.
MrTenuki: I'm not sure if in the second diagram is correct, because black could resist like this:
If white plays at a, black can connect the stones safely in a manner similar to that of Case A. If white plays at c...
And it's a ko ( at e). Sure, white takes first and will most likely win the ko, but why start a ko when you can capture unconditionally?