"Knock, Knock, Knock".
This is no longer first contact in our lore.
And USCM enlistement rates are already struggling as entire Falling Falcons battalion is a penal one. Criminals, religious fanatics (like myself), rookies, conscripts, disabled, nearly insane, too dangerous to be around normal troops etc.
However there is no point in micro-bombing marines. Cynadine pill in tooth, or something like that works wonders and it's spy-era "tech", nothing too hard.