During Tatsumi's execution, Syura came back from the dead after Dorothea experimented on his dead body. It made him more powerful and dangerous. He used that new power of his to remake his Shamballa Imperial Arms and kill his father, along with young emperor Makato. Seeing as he got so strong, both sides knew that they had one goal in common. Work together and everyone will survive. After this little 'war' ends, they will be enemies again.