Let's move one row backward and not toward one side since these icons are paired up. So in the next row we can find Saint George (not the blue outline of his halo) and Saint Demetrius (of Thessaloniki) both of whom are military saints/martyrs.
The difference is that Saint George personally fought the Dragon - which in another thread (probably about Satanism) we "established" is Satan himself - just as the dude one row before him: Michael fought with Satan.
Saint Demetrios on the other hand often considered to fight against the enemy of Christianity via proxy: there's a story that one gladiator killed many Christians and Demetrios converted another gladiator, who - aided by his newfound faith - killed the heathen opponent. So he has an aspect that is in line with Gabriel's, both of them are the men of the Word.