They are Batto's Messegers.
When the Ōu invasion started, Batto had 2 personal messengers he keeps with him. When something went wrong, he sent his first messenger to tell his soldiers what is needed. But when the plan fails, he sends his second messenger to tell the soldiers that surrending ain't an option. Unlike the first one, the second one was stopped by Kurotora before he got there.
Also, there was another messenger out on the battlefield who worked for Batto. He was a small dog who stayed up in a tree, tapping morse code with a stone to Batto.