In simple words, life expectancy refers to the total number of years an individual is expected to live in a particular conditions and environment of a country. This is seen as a measure of the development of a country and is usually seen to be high in developed countries.
Initially governments focused only on saving the young population from disease but now the authorities are taking steps for continuous healthy life style so that one can live for more years.
Assuming you're referring to the American Revolution, the revolutionaries felt they were in danger because the British far outmatched them in terms of man power and skill. To remedy this the colonists turned to foreign aid, especially from the French.
