Anecdotal evidence suggests that the Primarch Horus often adopted new squad formations having seen their effectiveness in other Legions. Early on, during the early years of the Great Crusade, it is said that the then-Luna Wolves Legion had a low number of shield-equipped Breacher Squads within the XVI Legion. The contribution and success of such units amongst the Imperial Fists' forces did not escape Horus' notice. After the annihilation of the xenos Latrical during the Imperial campaign known as the Latrical Onslaught, the number of such squads in the ranks of the Luna Wolves rose noticeably.