You carry humanity's survival on your shoulders. Train your children well.
The most obvious anti-alien group is Space Force.
Think about it. Lets wonder if Space Force needs to implement comprehensive strategies to prepare for potential alien threats.
For example:
1. Scenario Planning -- Regular war games and simulations to prepare for various invasion scenarios.
2. Alliances and Collaboration -- Partnering with other nations and possibly private space companies to pool resources and knowledge.
3. Rapid Response Teams -- Highly trained units ready to respond to any extraterrestrial threat at a moment's notice.
Who knows about guided missiles?
Spoiler:
Laser Beam to the face!