If you're interested in the 'Observed Strategic Tendencies' of the Legions, here they are;
Dark Angels: Combined arms and multi-spectra warfare, Exterminatus and purgation campaigns, extended independent void operations.
Emperor’s Children: Combined arms warfare, the use of complex manoeuvre and discursive tactical planning, asymmetrical assault.
Iron Warriors: Siege warfare, coordinated mass-theatre warfare, armoured assault, planetary decimation, attrition, retribution and counterinsurgency campaigns.
White Scars: Shock assault, high mobility warfare, harrowing actions and extended unsupported operations within hostile domains.
Space Wolves: Shock assault, search and destroy, pursuit operations, punitive and excoriation campaigns.
Imperial Fists: Ship-borne assaults and boarding actions, defensive and fortification operations in extremis, stronghold assaults, the conquest and forced compliance of void-fairing civilisations.
Night Lords: Punitive actions, decimation, enforced pacification, terror assaults, psychological warfare.
Blood Angels: High intensity warfare, strategic decapitation strikes, planetary interdiction campaigns, multi-vector and sub-orbital attack.
Iron Hands: Armoured and high intensity warfare, line breaker attacks, planetary pacification and suppression campaigns, anti-materiel operations.
World Eaters: Shock assault, planet-killer and Exterminates operations, close-quarters actions (space hulk purgation, boarding operations, line breaker attacks, ‘forlorn hope’ objective assaults).
Ultramarines: Mass assault, targeted decimation, planetary interdiction, liberation and limited theatre compliance campaigns.
Death Guard: Heavy infantry assault, attritional warfare, hazard/death zone warfare, xenos eradication and purgation operations.
Thousand Sons: Psychic warfare, precision assaults, misdirection, lore culling, macro-coordination multi-theatre campaigns.
Word Bearers: Mass assault, policing actions, gnoetic purgation, suppression of ideological revolt.
Sons of Horus: Shock assault, harrowing actions and strategic decapitation strikes.
Salamanders: High intensity or asymmetric warfare, zone mortalis engagements, planetary interdiction, liberation and defensive operations.
Raven Guard: Rapid deployment operations, strategic interdiction operations, reconnaissance in force, guerrilla actions, low-collateral damage imperative compliance operations.
Alpha Legion: Surprise assault, sabotage, infiltration, insurgency and counter-insurgency warfare, multi-vector attack, interplanetary pursuit and decimation campaigns, and deep-range raiding operations.
These are just the different Legions' preferred methods of war. They could all perform a vast array of different military operations, but would often attempt to apply their particular methods of war when possible