Here the difference between invading or not invading is illustrated in a beginners' game. In the first applet White does not invade and loses. In the second the invasion gives a clear win.
The point it tries to make is well understood nowadays and so is the need of perceiving looming forced invasions before their inevitability becomes all too blatantly manifest. Early on the damage may be kept to a minimum.

no Sound
Broken canvas...
to move
0 0
group penalty

Invading too late ...