Text of Amendment:
No soldier shall, in time of peace be quartered in any house, without the consent of the owner, nor in time of war, but in a manner to be prescribed by law.
In the years leading up to the American Revolution, private citizens were required to house British soldiers in their own homes. Given the tension that existed between British soldiers and colonial citizens, this was an unpleasant situation that the founding fathers did not want to repeat.
Right to Privacy:
The Third Amendment was one of the amendments cited in Griswold v. Connecticut (1965) as evidence that the Constitution protects an implicit right to privacy.
The Posse Comitatus Act of 1878 prohibits federal troops from engaging in domestic operations except when authorized to do so by Congress or the Constitution. Although the Third Amendment does not directly address the principle of posse comitatus, it does provide a natural ideological precedent to it.
Engblom v. Carey (1982):
The Third Amendment has never been enforced by the U.S. Supreme Court, but was once addressed by the 2nd Circuit Court of Appeals. In Engblom v. Carey, the circuit court held that the State of New York had violated the rights of prison guards who had been evicted from their on-site residences and replaced by National Guard troops after going on strike.