Question

Which military action led to the start of world war 1

Answer 1

The assasination of arch duke Francis Ferdinand is one of the leading causes of WW1 ? Does that help?

Answer 2

While it was not truly an military action, it was mostly a political action, with the start of Austio-Hungary trying to annex Serbia, leading to the assassination of the leaders of Austrio-Hungary Archduke Ferdinand and his wife Sophie by a Serb Princip, who was against the annexation.

hope this helps