The war in Vietnam that the US was waging had more to do with stopping the spread of Communism, which had it happened, would have in a way made the USSR appear to come out ahead of the Americans.
In Iraq, the motive was primarily to ensure an uninterrupted supply of oil to the US. What Saddam Hussein was trying to change with making the Euro the currency in which oil was traded instead of the USD, and several other similar steps posed a threat to US oil security.
He had to be eliminated before he could succeed. And nothing better could be used to garner support for a war against Iraq than by creating fear among Americans that Iraq was going to use the WMDs it had against the US.
To clarify something with regards to post #2, there were no al-Qaeda in Iraq before the invasion, so the threat to our shores was also not a reality at that time, just like in Vietnam.
Similarities include the fact that we do not understand the culture very well, nor do we have enough people in our military who speak the language. The population is more sympathetic to the rebels in some areas than to us or the Iraqi government. The government is beset by corruption, just like South Vietnam's.
A key difference is that Iraq's rebels had much less in the way of foreign aid, and virtually none from nation states, and certainly nothing as valuable as constant as the Soviet support for North Vietnam.
This is a loaded question. Personally, I agree with what has been said above; however, I also see parallels between the fact that both conflicts have been drawn out entirely too long. Our troops, in my opinion, should have been brought home long before now (and long before they were back then, too).
Another similarity lies in the profits that individuals made in the two wars.
In Vietnam the military/industrial complex made profits; in Iraq profits were made by Haliburton.
Deception is definitely common to both wars (involvement of politicians as mentioned above). The exaggeration of the Bay of Tonkin was used by the government as an impetus to get the U.S. into the Vietnam war while the Weapons of Mass Destruction hoax in Iraq was used by the government to propel troops into Iraq.
Many years later Robert MacNamara, Secretary of Defense under Kennedy and Johnson, apologized to the American people for the Bay of Tonkin, the escalation of the war, and the involvement of the United States. Similarly, President George Bush admitted after the invasion of Iraq that no weapons of mass destruction were found there.
There is one major difference that I see right away. When we fought the Vietnamese, there was NO danger that they would be on our shores, causing the kinds of damage that we know can happen. The enemy in Iraq is much less clearly identified. We do know that somewhere in there are people who are intent on causing us immense damage. When we left Vietnam, there was no possibility that the government that took over would create a training ground for terrorists; just about anything could happen when we leave Iraq. I think that's the major problem with our leaving ... what will follow.
There are similarities as well. Each war was fought with involvement by politicans that may have made it more difficult to "win." Although there was initial support for the Iraq war, particularly in our search for WMD's, that support has gone the way of the support for Vietname, although I don't remember there being as much support for Vietnam as there was for Iraq because there was never the immediate threat that we felt after 9/11.
I'm sure there are people who will disagree with some/all of this. The Vietnam era was very confusing, and I will always remember that what you see is often dependent on where you stand.
They are similar because both wars ended up very unpopular. They are different because we learned from veatnam that you should have respect for our soldiers.
Even though the Iraq War was unpopular, most people still respect the military.
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Should we respect the military without question? What makes a soldier more special than a doctor or a lawyer?