starting a war

warfare

noun

/ˈwɔrfɛr/

[uncountable]

1 the activity of fighting a war, especially using particular weapons or methods air/naval/guerrilla, etc. warfare 

countries engaged in warfare 

see also biological warfare, chemical warfare,  

2 the activity of competing in an aggressive way with another group, company, etc. 

class/gang warfare 

The debate soon degenerated into open warfare.

starting a war

 declare/wage war (on someone/something) 

go to war (against/with someone)

 cause/spark/provoke/foment/quell unrest

 incite/lead/crush/suppress a revolt/rebellion
  
launch/mount/carry out a surprise/terrorist attack

 prevent/halt/represent an escalation of the conflict
  
be torn apart by/be on the brink of civil war 

enter/invade/occupy someone's territory

 lead/launch/resist/repel an invasion

 civilians in war

 harm/kill/target/protect innocent/unarmed civilians 

cause/avoid/limit/minimize civilian casualties/collateral damage

 impose/enforce/lift a curfew 

engage in/be a victim of ethnic cleansing
  
be sent to a concentration/an internment camp 

accept/house/resettle/turn away refugees fleeing from war

more info :  http://oaadonline.oxfordlearnersdictionaries.com/dictionary/warfare