President Trump will address the nation on his Afghanistan war strategy tomorrow at 9 p.m. from Fort Myer in Arlington, VA. It's one of the most consequential decisions of his presidency, and it comes after Trump met with his national security team on Friday at Camp David . Defense Secretary James Mattis said on Sunday, per Reuters: "I am very comfortable that the strategic process was sufficiently rigorous and did not go in with a pre-set position."The stakes: Should Trump order a withdrawal of U.S. troops from Afghanistan, advisers believe he'd all but ensure the Taliban completes its takeover of the country. Al-Qaeda and ISIS would be allowed to flourish, and you'd have a terrorist launching pad similar to, or potentially worse than, before 9/11.Trump's decision hasn't leaked; but I can illuminate some of the private conversations leading up to it, from senior administration sources and former officials close to the Pentagon:Trump's top national security advisers all agree the only way they'll win their missions in Afghanistan is to modestly increase troop levels, keep training the Afghan military, and keep a strong CIA and special forces presence to run aggressive counter-terrorism operations.Two missions:"Operation Resolute Support": While the Trump administration is explicitly repudiating both the idea and the phrase "nation building," ORS is a train, advise and assist mission to help the Afghan army fight the Taliban, an official tells me. It's meant to help keep the government from collapsing while reversing Taliban gains.Counter-terrorism mission — primarily to eradicate Al-Qaeda, ISIS-K and other terrorist groups from Afghanistan.Inside Mattis' thinking: The Defense Secretary has been using this line in meetings: "Mr. President, we haven't fought a 16-year war so much as we have fought a one-year war, 16 times."What Mattis means by that: Trump has already given Mattis the authority to increase troop levels in Afghanistan, but the Defense Secretary has refused to exercise that authority, believing that doing so without an agreed-upon strategy would be continuing the failures of previous administrations. Trump officials condemn the Obama administration for falling into a habit of asking each winter "what do we need to do this year to prevent total collapse?"Trump's team presented him with other scenarios — which everyone on the team agreed would lead to disaster. They included a gradual withdrawal of U.S. forces from Afghanistan (a continuation of what Obama was doing), and counter-terrorism-only options.What Steve Bannon wanted: Mattis and co. never took the idea seriously, but Bannon and Blackwater founder Erik Prince had been pushing for Trump to gradually withdraw the U.S. military from Afghanistan and replace it with private paramilitary forces to hunt terrorists.I'm told the Bannon strategy has never been part of the NSC paperwork, though the former chief strategist circumvented the official process and took his arguments directly to the president.Trump's instincts: The president has been blunt, telling his team that while he thinks the war in Afghanistan has been a disaster, and the U.S. is losing, he thinks total withdrawal would be bad. Trump saw what happened when Obama withdrew from Iraq and believes that doing so precipitously in Afghanistan would allow the Taliban to take over, and Al-Qaeda would be resurgent. You'd have bad guys in Afghanistan in league with bad guys in Pakistan who want to overthrow the country.Trump has told his advisers he's been shown the maps of Afghanistan, with the red on the map signifying the Taliban's presence in the country. He says that advisers show him the map in 2014 and there's a little bit of red. Look at the 2017 map and half the country's red, therefore "we're losing."The generals' response to Trump: You're right. But we're losing because the strategy has been terrible. We can turn this around. Bottom line: Trump has been reluctantly open to the generals' opinion and I'm told he doesn't want to be the president who loses the country to the terrorists.