If I join the United States military and I die as a result of fighting the Taliban or ISIS or another group like them will I die as a martyr and Allah will take me to Jannah-til-Firdeaus?
wa `alaykum salam,
No one can give such an assurance. Real jihad can only be done under the Caliph of the Muslims, who does not exist in this time. Best at this time, is to stay home and work on your own self (jihad an-nafs) because no country or people are today on Truth. For that reason our Shaykhs have made clear that only the appearance of Sayyidina al-Mahdi (as) can bring true justice and true peace and eliminate falsehood and oppression.