If you control a battlefield with only one unit (Thousand-Tailed Watcher), and during an opponent's attack you use Arcane Shift to banish and replay that unit, can you play it back to the same battlefield even though there are temporarily no units there?

Ruling: Yes, you can play the unit back to the same battlefield. You cannot lose battlefield control as long as a combat is ongoing, and as long as you control a battlefield you can play units there.

Sequence:

• Opponent attacks into your battlefield
• You play Arcane Shift targeting your only unit at that battlefield
• The unit is banished (battlefield temporarily has no units)
• You play the unit back to the same battlefield for free
• You still control the battlefield throughout this process because combat is ongoing