The Telegraph has this headline:
Brutal details emerge of India soldier 'ambush' on contested border with China as Modi tries to calm tension
Should India used there be replaced by indian?
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You would have to refer to the paper's styleguide, but my suspicion would be that it's a way of compactly and specifically saying that the soldier is part of the Indian army.
An "Indian soldier" might work for any country's military, as "Indian" is an adjective that might be referring to the soldier's heritage, or a number of other meanings, while "India solder", while stilted, better indicates that this person was operating as part of the military of the country of India.