How bad can use of nuclear weapons be?  We have enough to destroy the entire planet!  Russia does too!  Many other countries have enough nukes to do significant carnage in the world.

"Trump’s Nuclear Arsenal"
The Damage Trump Can Do
With 4,000 Nuclear Warheads
By THE EDITORIAL BOARD OCT. 26, 2017

https://www.nytimes.com/interactive/2017/10/26/opinion/trump-nuclear-arsenal.html

"When Trump takes office in January, he will have sole authority over more than 7,000 warheads. There is no failsafe. The whole point of U.S. nuclear weapons control is to make sure that the president — and only the president — can use them if and whenever he decides to do so. The one sure way to keep President Trump from launching a nuclear attack, under the system we’ve had in place since the early Cold War, would have been to elect someone else."

So now we have a raving megalomaniac with the codes!

"

Former Defense Secretary Robert McNamara defined the strategy as the ability to kill one-quarter of a country’s population in a nuclear attack. The Natural Resources Defense Council used this measure to calculate the nuclear yield required to “decimate” several countries, providing a sense of the payload unleashed in such an attack.

Guaranteeing “mutually assured destruction” would require launching dozens, if not hundreds, of warheads on a target’s densest population centers. The N.R.D.C. calculated such an attack on China would kill 320 million people by targeting 368 population centers around the country – a scenario of such vast carnage, it can scarcely be imagined."

 . . . except by a megalomaniac such as Donald "Tweety Bird" Trump.

"The United States has a two-man rule in place at the nuclear launch facilities, and while only the president can order the release of nuclear weapons, the order must be verified by the Secretary of Defense to be an authentic order given by the president (there is a hierarchy of succession in the event that the ..."

https://en.wikipedia.org/wiki/Nuclear_football

"No one can stop President Trump from using nuclear weapons. That’s by design."
 The whole system is set up so the president — and only the president — can decide when to launch.Alex Wellerstein    December 1, 2016
https://www.washingtonpost.com/posteverything/wp/2016/12/01/no-one-can-stop-president-trump-from-using-nuclear-weapons-thats-by-design/?utm_term=.2ab252495388

WHY!?  What sane person would allow one (1) person even if it is the President o the United States,  to order a nuclear war!?

This is insane!  We are INSANE!