What specific event started world war 1

- What event started world war 1
- What event started world war 11
- What event started world war 1 in europe
- What major event started world war 1
- What single event started world war 1 in europe
- What key event started world war 1
- What specific event sparked world war 1
- What event officially started world war 1
- What event finally started world war 1