Modes
Gathering Storm
Rise and Fall
Cities
The World
Combat
Introduction
Declaring War
War Weariness
Ending a War
Unit Combat Statistics
Line of Sight
Combat Bonuses
Experience and Promotions
City Combat
Conquering a City
Formations
Pillaging
Air Combat
Unit Movement
Science and Technology
Culture and Civics
Gold and the Economy
Faith and Religion
Diplomacy
City-States
Trade
Governments and Policies
Great People
Nukes
Tourism
Victory and Defeat
Teams
Declaring War
Declaring War
There are a few ways to declare war. The first requires you move a military unit you control into another civilization's unit. This will prompt a pop-up message to appear asking if you want to start a war. Alternately, war can be declared in the Diplomacy Window. Within that window, you will always have the option to make a surprise declaration of war, except against your declared allies. Your civilization will suffer a costly 
Grievances penalty if you make a surprise declaration of war. To avoid some of this penalty (but not all), denounce the offending civilization and soon the option to formally declare war will appear in the Diplomacy Window.
You will also declare war against the target of a Military Emergency, City-State Emergency, Nuclear Emergency, and Betrayal Emergency, if you join that Emergency.
Grievances penalty if you make a surprise declaration of war. To avoid some of this penalty (but not all), denounce the offending civilization and soon the option to formally declare war will appear in the Diplomacy Window.You will also declare war against the target of a Military Emergency, City-State Emergency, Nuclear Emergency, and Betrayal Emergency, if you join that Emergency.
Declaring War
There are a few ways to declare war. The first requires you move a military unit you control into another civilization's unit. This will prompt a pop-up message to appear asking if you want to start a war. Alternately, war can be declared in the Diplomacy Window. Within that window, you will always have the option to make a surprise declaration of war, except against your declared allies. Your civilization will suffer a costly Grievances penalty if you make a surprise declaration of war. To avoid some of this penalty (but not all), denounce the offending civilization and soon the option to formally declare war will appear in the Diplomacy Window.
You will also declare war against the target of a Military Emergency, City-State Emergency, Nuclear Emergency, and Betrayal Emergency, if you join that Emergency.
Grievances penalty if you make a surprise declaration of war. To avoid some of this penalty (but not all), denounce the offending civilization and soon the option to formally declare war will appear in the Diplomacy Window.You will also declare war against the target of a Military Emergency, City-State Emergency, Nuclear Emergency, and Betrayal Emergency, if you join that Emergency.
