Just what possible futures did Doctor Strange glimpse when he used the Time Stone in Avengers: Infinity War? For centuries - perhaps even millennia - the Time Stone has been the greatest weapon of the Masters of the Mystic Arts. The Ancient One herself used the Time Stone to explore the future, identifying potential threats and discovering the best way to defeat them. But she couldn't see beyond the moment of her death, content only to believe that her successor, Stephen Strange, would keep the universe safe.
Doctor Strange used the Time Stone for the same purpose in Avengers: Infinity War. While Iron Man, Spider-Man, and the Guardians of the Galaxy bickered, Stephen Strange used the Time Stone to explore all the possible futures and try to learn how to win. To his horror, he glimpsed 14,000,605 different futures - and there was just the one in which Thanos was defeated. Thanos would later claim to be "inevitable," and Doctor Strange would have been able to attest that he almost was.
Joe Russo, co-director of both Avengers: Infinity War and Avengers: Endgame, has confirmed that Doctor Strange's visions began with alternate versions of the Titan battle. Taking part in a Q&A in China, he was asked why Doctor Strange didn't use a portal to cut off Thanos' hand just as he had Cull Obsidian's. "Thanos' skin is almost impenetrable," he pointed out. "We don't know whether Doctor Strange had the capability to do it... Doctor Strange realized this issue during his millions of test runs." Presumably Strange explored lots of other versions of the Titan battle as well, and realized the heroes were destined to be defeated no matter what happened. It's reasonable to assume that, in some versions, the fight ended more swiftly and Scott Lang never got stranded in the Quantum Realm - that timing proved essential to Strange's Endgame plan. Meanwhile, in at least one version Tony Stark must have died; Strange intervened at just the right moment to ensure he survived Thanos' wrath.
Incredibly, Russo has also revealed that Strange saw some timelines in which Scott Lang was never freed from the Quantum Realm - because the mouse failed to press the buttons that triggered the Quantum Tunnel and freed him. "The mouse saved the universe," Russo quipped. It's staggering to realize that Doctor Strange's 1 in 14,000,605 chance depended on the way a mouse's paws landed on the keys of a control panel. It gives a sense of just how near-impossible it really was to beat Thanos.
Strange himself may have seen millions of futures, but from that point on there are only two more that can safely be extrapolated on. Firstly, there must have been a timeline in which Strange told Tony Stark that he would need to sacrifice himself to defeat Thanos. Unfortunately, in that timeline, the foreknowledge weighed heavily upon Tony. Perhaps he took a moment to say goodbye to Pepper, or perhaps he lost his nerve for just a second. Whatever the case may be, Strange learned that telling Tony was a surefire way to ensure Thanos won, and as a result when asked he refused to give a clear response. In contrast, though, there must also have been another timeline in which Strange didn't raise his finger to signify to Tony that the time had come for their 1 in 14,000,605 shot. Presumably that led Tony to second-guess himself for a moment - inadvertently giving Thanos the chance to snap his fingers.
In truth, Doctor Strange's visions are a convenient narrative device. They give Marvel an easy response to any questions. Why didn't the Avengers try any other given tactic, or attempt to defeat Thanos using a different approach? Marvel's simple answer is that, if there were any other way, Doctor Strange would have seen it. Instead, the Sorcerer Supreme committed himself to a hugely improbable course of action that literally depended on a rodent's paws, a mad scramble for an Infinity Gauntlet on a battlefield, and a moment of sacrifice from Earth's greatest defender.
