Space debris forces astronauts on space station to take shelter in return ships
Some random comments on the Kessler syndrome [1]  * a Kessler syndrome would not impact Medium Earth Orbit and Geosynchronous orbit satellites. So, no, we would not lose GPS navigation. 
  * LEO satellites would be impacted, but at least Starlink claims to have a very advanced system of collision avoidance without humans in the loop [2] 
  * a Kessler syndrome would certainly not prevent an exchange of nuclear ballistic missiles. So, Kessler cannot be used in a defensive mode 

[1]https://en.wikipedia.org/wiki/Kessler_syndrome[2] https://space.stackexchange.com/questions/44765/starlinks-au...