I believe that it was the U.S army
The European balance of power broke down was an effect following German unification is correct answer due to fact that Germany (except Austria) was united by militarist state of Prussia with powerful army which definitely change balance on the European scene especially that formal unification took place just after end of Franco-Prussian war which humiliated France.
Determination of the south. They learned that the war wasn't going to be piece of cake and that it wasn't going to end within 3 months
<span> its A is the answer i think hope it helps </span>
Answer:
C. Trench warfare
Explanation:
A's incorrect as alliances have existed for thousands of years
B's incorrect as an infantry charge's greatest weakness is the machine gun for obvious reasons
D's incorrect as both sides had machine guns, and was not the reason for victory.
-----------
This leaves C, which makes sense as troops would be forced to hide on lower ground due to the deadliness of machine guns