Does Fortified Position's 'Shield 2' ability trigger when a unit arrives at an uncontrolled battlefield via surprise defense (after the initial showdown has started)?

Ruling: Fortified Position does not trigger on surprise defense. The battlefield must be controlled for its ability to trigger, and "you" on a battlefield always refers to the controller.

Nuances:

• If the battlefield is uncontrolled when a unit arrives via surprise defense, there is no controller to satisfy the "you" in the trigger condition
• This same principle applies to other battlefield abilities with "you" in their trigger conditions