Ten years after U.S. airstrikes on Baghdad punctuated the start of the Iraq war, nearly six in 10 Americans say the war was not worth fighting - a judgment shared by majorities steadily since initial success gave way to years of continued conflict.

Nearly as many in the latest ABC News/Washington Post poll say the same about the war in Afghanistan. And while criticisms of both wars are down from their peaks, the intensity of sentiment remains high, with strong critics far outweighing strong supporters.

See PDF with full results, charts and tables here.

A key reason: A substantial sense that neither war did much to achieve their goals of enhancing U.S. security. Only about half of Americans say either war contributed to the long-term security of the United States, and just two in 10 say either contributed "a great deal" to U.S. security - clearly insufficient, in the minds of most, to justify their costs in lives and lucre.

WORTH IT? - As such, 58 percent in this poll, produced for ABC by Langer Research Associates, say that considering its costs vs. its benefits the war in Iraq was not worth fighting; 56 percent say the same about the war in Afghanistan.

These results are dramatically different than they were when the wars began long ago. The war in Iraq, a few weeks after its start on March 20, 2003, was supported by 80 percent of Americans; in Afghanistan, in late 2001, support exceeded 90 percent. In neither case, it seems, did the public expect conflicts as long, as complicated and as costly as ultimately transpired.

Similarly, at the time of the fall of Baghdad at the end of April 2003, 70 percent of Americans described the Iraq war as worth fighting - nearly twice as many as do so today.

Nor did the war go over well in Iraq, as shown in a series of six exclusive polls there by ABC and other media partners from 2004 through 2009. Never did a majority of Iraqis support the U.S.-led war; by 2009, given the toll of the invasion and ensuing years of violence, 56 percent said it was wrong for the United States and its coalition allies to invade.

LESSON - The course of U.S. public opinion underscores a consistent political lesson: Hell hath no fury like an unpopular war. Public rejection of the Iraq war, in particular, irreparably damaged the presidency of George W. Bush; declining support for the war and Bush's falling approval rating across his second term correlated almost perfectly - at .95, with 1 a perfect fit. That's perhaps an impetus for the Obama administration's efforts to wind down the U.S. presence in Afghanistan.

Criticism of both wars has been higher than it is currently, likely reflecting the U.S. departure from Iraq and the reduced intensity of fighting in Afghanistan. In April 2007, at the height of the post-invasion conflict in Iraq, a peak of 66 percent called that war not worth fighting. Just less than a year ago an identical two-thirds said the same about the war in Afghanistan.

SECURITY - As noted, views of the wars' contribution to security strongly influence these assessments. Just 21 percent say the war in Iraq contributed a great deal to long-term U.S. security; among them, 70 percent say the war was worth fighting. Among those say the war contributed "somewhat" to security, 59 percent say it was worth it. But among those who say it didn't enhance U.S. security at all, a vast 83 percent say the Iraq war was not worth fighting. The breakdowns on Afghanistan are almost identical.

In terms of intensity, 43 percent of Americans feel "strongly" that the Iraq war was not worth fighting, more than twice as many as the number who feel strongly that its benefits did justify its costs, 19 percent. The divisions on Afghanistan, again, are very similar, 38 strongly critical vs. 18 percent strongly in support.

There are lingering political and ideological differences in views on Iraq, with support much higher among Republicans and conservatives compared with others. Fifty-seven percent of Republicans and 55 percent of conservatives say the war was worth fighting; just 35 percent of independents and 27 percent of Democrats, respectively, agree, as do just three in 10 liberals and moderates alike. Results on Afghanistan are similar among partisan groups.

HISTORY - The change in attitudes on the Iraq war, in particular, in many ways sealed the fate of George W. Bush as the most unpopular second-term president in political polling dating back nearly 80 years. Support for the war ebbed after the fall of Baghdad passed, yet the conflict continued; as noted, Bush's popularity faded with it.

By February 2004, just short of a year after it started, 50 percent of Americans said the war was not worth fighting; it reached a majority that June and stayed there, with just three exceptions, in 52 ABC/Post polls across the ensuing nine years.

In one notable exchange, in March 2008, ABC's Martha Raddatz asked then-Vice President Dick Cheney about the public's dissatisfaction with the war. Cheney said: "You cannot be blown off course by the fluctuations in the public opinion polls." At that point, about six in 10 Americans or more had described the war as "not worth fighting" continuously for two years.

Today, five years later, nearly six in 10 still do.

METHODOLOGY - This ABC News/Washington Post poll was conducted by telephone March 7-10, 2013, among a random national sample of 1,001 adults, including landline and cell-phone-only respondents. Results have a margin of sampling error of 3.5 points, including design effect. Partisan divisions are 33-25-35 percent, Democrats-Republicans-independents.

The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by Abt-SRBI of New York, N.Y.