Only enclosed groups can be killed
Also the idea is:
To the extent feasible -- Avoid Becoming Enclosed
To counter an enclosure threat --"If In Doubt, Run Out."
Because only enclosed groups can be killed,-- There Is Little Value In Playing “Inside” Moves Against An Unenclosed Group.
It’s usually better to play outside moves, and force your opponent to make eyes and "live Small"
These principles are not absolute! There are circumstances in which the global position makes it more advisable to strike first at the opponent’s key shape point(s) to prevent an easy two eyes, and then profitably harass the fleeing group as it struggles to either connect or secure its eyes in the center.