Complex sentence: After the War was over, poverty forced people to wash off the cancels from the stamps and attempt to use them over again, such that the Government decided to put an antitheft device onto the stamps known as a grill.
Split into simpler sentences: After the War was over, poverty inspired people to wash off the cancellation from the stamps and attempt to use them again. The Government then decided to put an antitheft device onto the stamps known as a grill.