What to do if a raise was promised, but it didn’t happen?

Q: “Upon occasion I have come across an issue where a manager communicates to an employee in writing that they will receive a specific increase to their base salary, but then the organization is not able to come through. Does the employee have a legal remedy in this scenario, and other than ‘forcing’ the employer to pay whatever amount is owed, are there additional risks the organization faces if they don't deliver on what was committed to the employee?” – Lara, New York