In Panzer General II , losing a core unit with a leader is downright excruciating. Unfortunately, one thing that hasn't changed very much in the new game is the supply rules. The unrealistic automatic resupply of the 5-Star Series has migrated to the new game. So a unit isolated behind enemy lines can still be fully resupplied. At least in the new game the rules for deploying newly purchased units have been revised in favor of realism.
New units can no longer enter in hexes around any captured city.
Instead, they may only enter in the hexes around designated supply hexes. There is another rule change in favor of realism that is addition by subtraction. In the 5-Star games you had the choice of purchasing ordinary replacements that had the effect of reducing the overall experience level of the unit or more expensive elite replacements that did not reduce unit experience. In PG2 there are only ordinary replacements and the unit retains its experience leve no matter how many you purchasel. This change in favor of simplicity also strikes me as a change in favor of realism.