Full writeup and cards at BGG link below:

https://boardgamegeek.com/article/22631873#22631873

DOMINATE ABILITY: After resolving your dominate order, you may perform a free restricted deployment. You may purchase a minimum of two units all of the same type for a cost of 1 less than normal, per unit. Deploy these units onto a single planet with a factory in the active system.

“ We have more soldiers than you have bullets ” sums it up for the guard. The guard has an enormous capacity to pump out units with its dominate ability, particularly guardsmen for half price, and most of their combat cards depend on having combined arms in their battles. The Guard’s strategic issue is getting those different units to where they need to be, because their dominate ability only allows units to be spammed en-masse to a single planet. To feed their war machine, particularly when spamming guardsmen, they need to hold a fair amount of material producing territory, because cache tokens are wasted on spamming 1pt guardsmen.

Unit Mix

12 Guardsmen
3 Cruisers
6 Ogryn
6 Leman Russ
3 Battleships
3 Titans

The effectiveness of the Guard’s combat cards is maximized by fielding combined arms - using multiple types of units in the same army, leading to the whole performing better than the sum of the parts. An effect that is required because Guardsmen have the worst stats in the game. Not only that, but the effect of the combined arms is only realised with unrouted units - its no use having a card that benefits from combining unrouted tanks and unrouted guardsmen if your only tank gets routed in the first round. So rather than routing your last heavy unit to tank damage, you will find it more useful to use some guardsmen as ablative meat shields rather than routing that heavy, and thereby ruining the effectiveness of its armies. Guardsmen are both vital and completely expendable.

The Guards combat deck has a number of cards that are more effective the more guardsmen you field, and the opposite is also true - if you dont have many guardsmen, those cards become underwhelming. Try to have a couple of cards in your deck that are not so dependent on massing guardsmen, to give you more options when defending or in later rounds of combat when your guardsmen have been killed.