In 1971 the Pentagon Papers were disclosed to the public. They revealed that the Johnson Administration had “systematically lied, not only to the public but also to Congress” about the Vietnam War. 
Just one month ago the Washington Post disclosed government documents revealing that “senior U.S. officials failed to tell the truth about the war in Afghanistan throughout the 18-year campaign.” 
We’ve also known for years that we were lied into a war in Iraq when the U.S. failed to discover the so-called “weapons of mass destruction” the neocons in the Bush Administration were fear mongering about. The Center for Public Integrity reported that “President Bush and top administration officials made more than 900 false statements in the two years following Sept. 11, 2001, about the national security threat posed by Iraq under Saddam Hussein…. The statements by Bush, Vice President Dick Cheney, then National Security Adviser Condoleezza Rice, former Defense Secretary Donald Rumsfeld and other officials ‘were part of an orchestrated campaign that effectively galvanized public opinion and, in the process, led the nation to war under decidedly false pretenses.'” 
Now we have the Trump Administration claiming that we were facing an “imminent” threat from Iranian general Qasem Soleimani to justify the U.S. strike that killed him last week. YET they haven’t provided ANY evidence of that claim to Congress. 
While, for now, it appears that we may be backing off from all out war as a result of Iran’s measured and limited response, tensions have increased and the least little thing might trigger a very deadly conflict. 
In 2002 the U. S. Armed Forces conducted a $250 million war game against Iran called “Millennium Challenge 2002.” It was supposed to last 14 days, but the retired Marine Corps general they picked to command Iran’s (“Red”) forces basically wiped out most of the U.S. Navy (“Blue” forces) in that area in a strike on the first day (which would have resulted in the deaths of over 20,000 U.S. service personnel).
The game was suspended and restarted, and the participants were ordered to follow a script drafted to ensure a victory of U.S. (“Blue”) forces. In objection to the new script restricting him, the retired general complained and resigned from the game. 
This is not saying what might happen today in a real conflict with the current actors, and possibly things have been learned since then, but Iran’s forces are supposedly 4 times greater than what the U.S. faced in Iraq, and that conflict resulted in the deaths of hundreds of thousands of people on both sides, cost trillions of dollars, and we’re still involved in a conflict there 16 years later. 
In other words, a war with Iran would likely not be as quick and easy as some are saying, and we shouldn’t automatically believe ANYTHING coming out of the mouths of Trump, his administration, senior U.S. officials involved in the military industrial complex, war mongering representatives in the House or Senate, or war mongering pundits on cable.
Another thing to keep in mind is that there are a group of neocons who have been pushing for conflicts like this for many years now (going back as far as the George H. W. Bush Administration). They were behind the War in Iraq during the George W. Bush Administration and they still have a lot of influence. John Bolton is just one of them. 
8. Iraq War