In military forces, leave is a permission to be away from one's unit, either for a specified or unspecified period of time.
Various militaries have specific rules that regulate leaves.
British troops in World War I received leave for "Blighty" every 15 months.
A furlough is an extended period of leave from front line service in order to return home.
For example, during World War II New Zealand soldiers who had served overseas for long periods (usually three or more years) were granted a "furlough" for a visit home.