Caretakers

The war is over, declared the machines.
Sensors watched the radiation levels drop.
When they were low enough, probes went out to scan the planet for signs of life.
Not much, but some.
The machines gathered up what they could.
As cleanup systems went to work on the ruins, genetic templates kept in storage were imposed onto the surviving organics to undo the ravages of mutation and gamma-ray damage.
Some genetic lines died. Some survived.
As each landmass was declared safe, replanting and restocking routines seeded the planet with life again.
The machines sank under the oceans and shut down.