These house rules are meant to make the game more realistic while staying as simple as possible.
Battleships cost 14 IPCs. They cost 1 IPC to repair.
Switzerland has an IPC value of 4.
The U.K. can only produce up to 4 units per turn in India. If India is captured by the Central Powers, the Central Powers cannot produce units there.
If a capital is captured, the IPCs are discarded and not taken by the capturing power.
Neutral territories that are not home territories still get units if invaded.
Sea units, except submarines, must end their movement when they enter a sea zone with enemy mines.
Units that retreat from a contested territory cannot move into another contested territory. They may move into any adjacent friendly territory.
There is a combat move and a non-combat move. During the combat move, units can move into neutral, contested, and enemy territories. The non-combat move comes after combat. During the non-combat move, units that did not move during the combat move and did not conduct combat can move into friendly territories. Land units can move an unlimited number of territories during the non-combat move within their original territories.
Optional Manpower Rule
Keep track of the infantry that are destroyed for each power. If a power has had 2x the number of their infantry destroyed as their starting IPC value (rounded up), they may only collect half of the total IPC value of their territories when they collect income (rounded up). If a power has had 4x the number of their infantry destroyed as their starting IPC value (rounded up), they may only collect the IPC value of their capital territory when they collect income.