It means with a fiery passion for violence, hatred, etc.
In this case, it sounds like it would belong in this kind of sentence:
"The ruthless general came back from his leave with a marvelous new militancy, and was eager to get back into the action of killing the enemy."
It has a sadistic connotation, it seems.
Answer:
The meaning is that of the strength of purpose and determination.
Explanation:
