Answer:
When this is found in a road you are forced to make a decision.
My second is performed by my first, and it is thought a thief by the marks of my whole might be caught.
Useful term for when you need to start a fire or notice someone with the same shirt as you.
Soldiers fight it but never changes.
I'm a ring of sliced onion dipped in batter and then deep fried.
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.