Don't run 2 and 2 - run 4 and 4.
Each player has 2 PCs, played on alternating sessions. When focused on the mines, everyone uses the prisoners. When focused on the covert military operation, everyone uses soldiers/spies/operatives.
At some point, you'll have a mingling of the groups (the breakout). Simply let everyone pick one PC after the breakout succeeds/fails and that's your ongoing four person group.
Each player has 2 PCs, played on alternating sessions. When focused on the mines, everyone uses the prisoners. When focused on the covert military operation, everyone uses soldiers/spies/operatives.
At some point, you'll have a mingling of the groups (the breakout). Simply let everyone pick one PC after the breakout succeeds/fails and that's your ongoing four person group.
