Basic Trope: Backwards threat level scale where higher numbers mean war.
Straight: DEFCON 1 is the lowest level of military readiness and DEFCON 5 is the highest.
DEFCON 6,000,000 is the highest level of military readiness.
DEFCON 0 means unilateral disarmament and disbandment of the military.
Justified: The government changed the system because it confused too many people.
Subverted: With the world on the verge of nuclear war, the President orders the country to DEFCON 5. It's then revealed that the crisis had just been resolved off-screen.
Double Subverted: But the President didn't know that at the time.
Parodied: In the middle of a national crisis in a Dr. Strangelove-type movie, the President and his staff waste valuable time arguing over whether the DEFCON numbers go up or down.
Zig Zagged: On the verge of World War III, the president orders the US to Defcon 11. It turns out that he means he is going to relinquish the military and declare the US once again a colony of Great Britain.
Averted: DEFCON 1 is correctly given as the highest level of military readiness.
Defied: The President explicitly asks his military advisors what ordering DEFCON 1 means before he gives the order.
Deconstructed: After a nuclear crisis is averted, President Buffoon orders the country to DEFCON 1, thinking it means peace. The military takes this to mean the crisis was not averted, leading to A Nuclear Error and World War III.
Reconstructed: Centuries after the nuclear hellfire, new countries with sophisticated militaries arise that adopt a DEFCON scale.
Played For Laughs: President Buffoon describes the DEFCON level as "over 9000". He's the only one that finds it funny.
Played For Drama: With the country currently at DEFCON 3, the government doesn't know what the President meant by "Go to DEFCON 4" before communications suddenly cut off without explanation, as he has been confused by the DEFCON system before. Did he mean "raise the military readiness" or "stand down"? Get it wrong one way, and the nation is vulnerable to attack; get it wrong the other way, and they may raise tensions to the point of A Nuclear Error for no reason.