1. return to the start (usu. after failure), come/turn full circle
go/went back to square one
This expression refers to the need to revise or begin something again, typically as a result of a previous failure. Its use is very common in a professional context, where it is usually said after a setback. The need to go 'back to square one' may arise as a result of a failure, but it often provides the opportunity to learn important lessons and then come back stronger, and more successful than before. For that reason, the term does not always have a negative connotation. A phrase with a similar meaning is 'back to the drawing board.'