1, normal communication, not a war zone.

2. Military communications and war zones, such as military mail and occupied area stamps.

3. Special communications and war zones, such as "draft" stamps.

4. Political propaganda, in addition to internal propaganda, also propaganda to the enemy: During World War II, the Allies and Axis countries "tampered" with each other's stamps and then put them in each other's area.

As a currency, the Soviet Union used small stamps as tokens (it seems that it was not wartime).

6, turned over to the state, in exchange for foreign exchange, the Soviet Union also happened.

Use the rest if you want.

If you want a more detailed paper, send me an 80-edition Golden Monkey.