Environment- everything around you
The 16th amendment to the United States constitution allows congress to levy a tax on income.
Hegira
Hijrah also called Hegira is the migration or journey of the Islamic prophet Muhammad and his followers from Mecca to Yathrib, later renamed by him to Medina, in the year 622.
I would say the invention of new technology such as the tank, machine guns, and other weapons made every attempt to gain yardage in trench warfare very bloody costing hundreds of lives for every yard gained or lost.
