Responsibility Without Authority, How Does A Sales Manager Succeed?

The Situation
The ABC Company’s VP of Sales is responsible for ensuring the company’s annual revenue budget is achieved. However, this VP has no direct reports. Each of the ten salespeople report to facility general managers spread throughout the country. Thus, the revenue target resides with on the VP of Sales shoulders, but he has to rely on the GMs to manage the salespeople.
Your Challenge
What is the best strategy for this VP of Sales to employ to ensure the revenue budget is met?