Answer :
Only a few generations have been granted the
role of defending freedom in its hour of maximum danger.
By saying that “few generations have been granted” President John F. Kennedy communicates the sentiment that it is a privilege (or gift) that the current generation has that its freedom threatened because in such a case the generation would be obliged to defend its freedom. As such, by saying the phrase “few generations have been granted” puts a positive spin on the idea/notion of fighting for and defending freedom.
Only a few generations have been granted the role of defending freedom in its hour of maximum danger.