Generalist formations and the cost of specialization

Are the Ultramarines mainly a garrison formation?

Not exactly. They are broad generalists who can handle most missions competently, while more specialized formations excel more narrowly but depend on other forces to cover their weaknesses.

The Ultramarines are described as an adaptable formation able to perform most missions competently without dominating any one role. Other broadly capable loyalist formations combine that flexibility with particular strengths in assault or defense. More specialized forces can achieve greater excellence in a narrow task but need other organizations to cover their weaknesses. The comparison presents a familiar military tradeoff between general-purpose resilience and specialist dependence.