Stratagems have a special role in this campaign. There is no CP, but Stratagems are connected to veteran units and hq to represent their skills and expertise.
For you HQs the following effects apply:
You have a number of stratagems permanently attached to your warlord. Each of the stratagems can be used once pr battle. Each stratagem can be played on all eligible units in your force for free. Certain upgrades for your warlord can make the stratagem affect ALL eligible units in the army. But either way you have to pick the moment to apply these special skills.
Space Marine captain Exemplus has a warlord trait (The Imperium’s Sword) and the stratagems Transhuman physiology, Smokescreen and Unyielding in the Face of the Foe. This indicates this is a warlord who focus on defensive tactics and drill his forces with these skills. During the battle he can use each of the stratagems once. directed at any eligible unit. But his warlord trait is always active as stated in the rules. As his experience grows his skill level and stratagem selection increases.
After a long series of battles fought captain Exemplus has gained more knowledge. He even won a decisive victory where he used his defensive stratagems. Now he can upgrade one of them to be "army wide". Meaning that when he choose to use "Transhuman physiology" it will affect all eligible units in his army for the active phase.
For you non-HQ units the following effects apply:
A veteran unit get a personal stratagem available. They can use it once at any point during the battle, but it can only affect themselves / their target.
How to gain veterancy
The best way to gain veterancy is to survive a battle where the unit accomplished what they set out to do, or saved the day in a way.
Units that survive should be included in the battle report - and they may gain veterancy.
Making it clear to your oponent what is available.
Stratagems and veteran units are cool - but make sure it's clear to your opponent what options are available and avoid "gotchas"