+6 Infantry to be placed in either the territory being attacked by Japan/Russia, divided between the territories being attacked by Japan/Russia (split as the defender sees fit) or placed on the capitol of the defending nation. Infantry are awarded after the combat move phase but before the combat phase. Defender has discretion on how and where the infantry will be placed, given the restrictions above.
Example: On Russia 1, OOB 1940 global, they attack Korea. Korea has 1 infantryman defending it, so Japan decides to add 6 more to the territory making Russia fight 7 defensive infantrymen.
For those who want “realism” call it outraged Militia men. Boys no older than 13 winters and men younger than 70 winters grab the rifles they use to hunt/protect against animals and conduct nhuissance attacks against the aggressor.