Accountability and responsibility — both are important, but they are NOT the same thing.
An accountability is an end result. Being accountable is being answerable for a result.
For example, a primary accountability for a customer service manager might be to “ensure that all customers are satisfied with their company interactions.” The manager is never completed with this result, and it involves many activities and many smaller results such as answering calls within three rings. The manager is accountable for the ongoing achievement of that result by many means.
A responsibility is an action. To be responsible is to be answerable for acting on some task or acting in a certain way.
For example, a manager is responsible for treating all employees with respect. To treat any employee without respect is to be irresponsible.
Both accountability and responsibility are important building blocks of strategy execution. Unfortunately, both are also misused such that they connote “guilt,” as in “Who is accountable?” and “Who is responsible?”