How did ancient homing pigeons deliver letters?

The carrier pigeon doesn't directly deliver the letter to the recipient, but returns to his hometown, where it is taken off the carrier pigeon's leg by a special person and delivered to the recipient. For example, homing pigeons are raised in place A, and when they grow up, they are taken to place B, and when they send letters from place B, they are taken back to place A by homing pigeons. (Don't be misled by TV and movies)

Because there was no better communication tool in ancient times, some foundry workers raised many pigeons. That is to start a home with pigeons. They have a strong memory. So some generals have to take some pigeons domesticated by the caster when they go out to war. As soon as there is something new, he will let go and report whatever he wants. Some people will inevitably return to the city. In this way, the caster will soon know the situation in the distance.

The other is that two casters or two families have some pigeons. When the two sides meet, they will exchange some pigeons with each other. When necessary, they will put some pigeons with letters. In this way, some pigeons will fly back to their homes and bring back important letters to their owners.