The religion is called birth, disease, old age and death, this applies to all. Well, death does any way. There are so many paths so many variables to consider in the world today that it is near impossible to say with 100% certainty that there is only one way. Faith is not knowing for a fact. Beief is not knowing for a fact, both have a tint of doubt, because as far as I know none of us were ther in the beginning. People make up stories all the time and things get rewritten as time passes.
You could also include the people who died thinking that Krishna/Vishnu is the Supreme personality og Godhead (mostly Hindus). Physical death is the real religion in the materil world. Even stars and planets die over time. What is beyond how will one know unless they have been there?
If people want to claim they are fighting for God, that is nice but the God, I know does not need anyone to fight on God's behalf. God send plagues, heartattacks, aids, cancer, earthquakes, volcano eruption, sunamies, tornadoes, etc to take care of the fighting business.