North Star Anti-Fleet Defenses Around the North Star System · 10:18am Dec 17th, 2015
Deep within the large military command headquarters on Þettaland, deep within the bowels of the facility, there lies humanity's second truly stable AI. Its comprehension spans the galactic sector's largest computer complex. In it's control lies the greatest defensive weapon humanity has ever conceived.
A defense system comprised by two simple things...
A enormous mass displacement FTL gate generator,
and billions of small rocks with control thrusters on them.