45 years into a recent game (my 5th game, 1st serious one). Also, first game I turned invaders on.
Aliens send 3 scouts into Sol from a dormant jump point, doing grav surveys. Contact made impossible, I shoot them down.
1 year later, another scout pops up from an already explored system.
I send a small battle group through and notice a wormhole. Immediately send it back packing to earth.
A day later, 3 alien ships follow the fleet through and destroys it with missile spam. 7 more jump in through the span of a day.
My mobile garrison of 6 cruisers gets reduced down to 1 by missile spam (21-36x missiles per salvo, dozens of salvos). I manage to destroy 7 ships with single high density (20x missiles) salvos at each ship (smaller amounts do negligible damage). Around half of these kills were possible because their ships ran out of ammo.
Large missile wave (+2k) with thermal signatures of over 9000 inbound to earth. 10 PDCs (400 short range (<25mil km) missile launchers total, no other offensive systems) barely stop it from reaching earth.
My final cruiser runs out of ammo trying to finish the remaining 3 ships off, slightly damaging one before it completely repairs itself.
It flees back to earth, with 3 pursuers attempting to ram it on a 15b km course to earth.
Garrison of PDCs at Earth destroy 2 ships. The remaining hostile kamikazes into a mega passenger freighter and takes it down with it.
Invader threat suppressed, for now. The wormhole is still in the nearby system.
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First time seeing invaders on my first enable. Passive aggressive is a good term for their behavior.