That’s cool down after a fight has been ended there. No new wars can declared at that spot, till that timer will be finished. So players from the team winning can rest there to regain energy or have time to get online. But they can definitely join any other war on a different tile.
A couple of conquests ago, this timer wasn’t there, resulting on teams who lost, immediately pinning a lot of players in one spot. There was no intention to win that war, nope. Intention was to keep those players locked, so that they couldn’t help in other wars. So that’s why cool down was introduced.