Which action completes this diagram

The use of machine guns resulted in massive casualties

Explanation:

On the western front, soldiers dug into trenches and would stay there until they were ordered to cross "no man's land". It was called this because of the machine guns, barbed wire, mines and the open field they had to get through to make it across.

Nobody wanted to cross no man's land because a single machine gunner could pin down and dispatch many soldiers in a short period of time. This resulted in long stalemates where neither side wanted to cross.

the protestant reformation's started in 1517, disturbing the religious and political order in europe´s catholic countries. the outcome was the european wars of religion prosecuted in europe in the 16th, 17th and part of the 18th century. nonetheless, uprisings, territorial disputes, and great power conflicts were also causes of the wars.  

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