With his every utterance, the invaders’plight became more apparent. The Primarch’s strategic acumen, his tactical genius and miraculous mental acuity were unmatched. The leaders of the Ultramarines looked on in amazement as Guilliman marshalled the defenders like regicide pieces,drinking in reams of strategic data and issuing a steady stream of orders that turned one fight after anotherin the defenders’ favour. Calgar and his lieutenants had executed a super-human campaign of defiance against the invaders, but the Primarch was operating on a different mental plane.

Rise of the Primarch, page 33