The pamphlet seeks to engage Americans in the fight against the British. Indeed, Paine wrote The American Crisis pamphlets during the early stages of the American Revolution that were very unfavorable to Americans and when their cause seemed more uncertain than ever. Support for the Revolution was waning and Paine intended to galvanize it in order to facilitate a turnaround of the current situation.
The analogy of winter intends to show the reader that as winter gives way to the new life of Spring, the initial struggles and defeats of the American Revolution would give life to victory. The use of the terms hope and virtue intend to show Americans that this was a just war against tyranny and that the alternative to victory was the death of democracy.