Note: this first part of the answer was written when the question only had the Chris Stewart quote; for more on the generals-disagreeing (WJS) issue, see below the line.
In other news: "Washington can't stop playing the blame game over the US's disastrous Afghanistan withdrawal". My summary:
- some say it's Biden's sole fault;
- some say it's the fault of the Trump and Biden administrations for withdrawing (somewhat conveniently forgetting that the US opinions polls favored this for a while);
- some say it's the incoherent US policy in Afghanistan in the past 20 years;
Etc. I mean if you want quotes:
In April, nearly 70% of Americans supported withdrawing US troops from Afghanistan following a 20-year conflict. This week, that number plummeted to 49% as the American public watched with horror as the Taliban marched into Kabul and desperate Afghans tried to flee the country. [...]
Robert Deitz, who previously served as the general counsel at the NSA and was a top lawyer at the CIA in the late 2000s, also attributed the swift crumbling of the Afghan government to policymakers' unwillingness to heed the intelligence community's warnings. [...] Deitz added that "both the intel and defense communities were aware about the Taliban's growing power over the last number of months. The fast collapse was not a surprise to the intel community. It is the policymakers who were surprised." [...]
Douglas London, the CIA's former counterterrorism chief for South and Southwest Asia London, who retired in 2019, added, "The decision Trump made, and Biden ratified, to rapidly withdraw US forces came despite warnings projecting the outcome we're now witnessing." [...]
"For a lot of us who served over there, the focus is more on just the incredible institutional failures," a former senior defense official told Vanity Fair. "The failure of the US military to build cohesive security forces, that's a 20-year failure. And I think we've got to look at that from a policy perspective and figure out what went wrong over a longer period of time."
As for the "ADDED" issue like the specific generals which opposed the withdrawal... here's what the Atlantic had to say in April:
Who lost Afghanistan? Generations of diplomatic and military historians will debate that question, and there will be blame to share among presidents, members of Congress, generals, and statesmen. Here’s an easier question: Who lost the debate over when to leave Afghanistan? The military did.
[...] As Biden weighed his options, top generals argued strenuously against a complete pullout, pushing for leaving a small force behind.
So it's hardly a (newly discovered) secret that many in the military top brass opposed a pullout, even if that was the majority of the US public opinion/choice, eventually reflect in the political leadership of the present and previous administrations...
And the "general override" isn't new either:
Trump had an unusually frosty relationship with both of his retired generals and the military leadership, even as he described himself as a pro-military president. Flynn was fired within a month of the inauguration in a Russia-related scandal. Kelly was promoted to White House chief of staff, and was happy to work with Trump where they agreed ideologically, but ultimately ended up deeply estranged from the president, who he thought was an unstable nut. Kelly left at the end of 2018, followed closely by Mattis. Mattis, too, had decided that Trump was dangerous, and according to the journalist Bob Woodward, he sometimes just refused to obey orders from Trump, including a demand for a strike against Syria’s president. But Mattis eventually resigned when Trump insisted on withdrawing U.S. troops from Syria, a decision with which the defense secretary, and most generals, vehemently disagreed. The brass also hated Trump’s claim that he’d withdraw troops from Afghanistan. [...]
General Mark Milley, the chairman of the Joint Chiefs of Staff, was reportedly in favor of keeping special operators on the ground in Afghanistan, in what has become the military’s favorite solution to every problem in recent years, as Mark Bowden reported in this month’s issue of The Atlantic. But when Milley was overruled, he got in line, and a spokesperson told Politico that “senior officers were afforded ample opportunity to give advice.”
The only difference may have been that Biden didn't fire generals (who disagreed with thim) left and right... And retired generals have been even more scathing of the Afghanistan withdrawal as they don't have to shut up to keep their job anymore...
The loudest protests have come from people such as David Petraeus, the retired general and former CIA director. “Ending U.S. involvement in an endless war doesn’t end the endless war,” he said Wednesday on a conference call, Defense One reported. “It just ends our involvement. And I fear that this war is going to get worse.” It’s probably no coincidence that Petraeus’s zenith came at a time when presidents of both parties deferred to top generals like him.
And as the US elections were unflooding in Nov 2020, NATO's secretary general went public with such criticism:
Amid reports that defeated U.S. President Donald Trump is planning a major withdrawal of forces from Afghanistan, NATO Secretary-General Jens Stoltenberg warned Tuesday against a hasty pullout, saying “the price for leaving too soon or in an uncoordinated way could be very high.” [...]
In his statement, Stoltenberg emphasized that NATO had planned to keep troops in Afghanistan to train, advise and assist Afghan security forces through 2024, even with expected, continuing U.S. reductions in forces.
Note that Stoltenberg is a (Norwegian) civilian/politician, but he surely had his [NATO] military advisers.
Going slightly further back, a similar situation (in the sense of generals registering their opposition) occured with Trump's withdrawal from Syria. It's honestly hard to think when generals didn't object to something like that, even during Obama's terms around issues of political promises of no "boots on the ground" [in Syria], etc.