This The Tomorrow War article contains major spoilers.
The key to a good time travel tale is that it must define its arbitrary rules and then stick to them. The Tomorrow War on Prime Video skillfully keeps it simple. However, there is a moment in the film where viewers might be tempted to shout at their screens when Dan Forester, the ex-military biology teacher played by Chris Pratt, appears to temporarily misunderstand how time travel works, even though elsewhere he’s got it figured out. Luckily, covering the basics should provide an explanation for Dan’s misguided actions.
Before watching The Tomorrow War, potential audience members may have asked themselves upon hearing the premise, “If you pull people from the past to fight your war, aren’t you depleting from the same stock that would fight it in the future?” Luckily, Dan and his fellow recruit Charlie figure this out early on: only those already dead before the war began can be drafted. Ignoring that they might have erased a few children born in the interim, it neatly eliminates the potential messiness of duplicate selves as well.
It also explains why Lieutenant Hart and her personnel from 2051 are so young: no one already born in our time can come back to train new soldiers. It’s admirably simple! Along those same lines, new recruit Norah should be applauded for asking why they can’t just be sent to a point earlier in the war to avoid impending human extinction. Describing the tethered rafts moving forward along a stream thirty years apart is an elegant illustration of time’s inexorable progression, and Dan seems to track with this as easily as most The Tomorrow War viewers do.
So why is Dan so intent on saving the future version of his daughter even after she explains what she wants to do with the toxin designed to kill the White Spike queens? Muri tells her father, “You need to make sure this never happens,” but he still says he’ll come back for her after he delivers the means to defeat the enemy before they even start to fight. Granted, it can’t be easy to see one’s offspring die in an alternate 2051, even if you know the 9-year-old Muri is waiting in 2021, but still, Dan understood the rules up until then and then hesitated needlessly.
Perhaps that’s the point the veteran Dorian was trying to make about Dan trying to save those already lost. But even so, Dan must surely want to erase the man who left Muri when she was 12, divorced her mom when she was 14, and died when she was 16. The travelers from the future pretty much took care of that simply by showing up, since obviously no one in elder Muri’s world remembers hearing about strange visitors appearing in the middle of a soccer match, even if it happened before they were born.
In fact, the rescued planet may have other things to worry about now. The world was in chaos, thinking that humanity’s fate was sealed, and that damage doesn’t heal overnight. Like the children of the pandemic, the kids in Dan’s class lost not just a year of school where there didn’t seem to be much point in learning, they also lost family members to a war that will now no longer happen. Those deaths can’t be undone even though they technically happened in a pruned branch of the future.
But even if Dorian would have died from cancer had he not made his sacrifice, Dan will almost certainly avoid dying in a car crash that very well may have been self-inflicted. We never heard how Charlie died young, but perhaps his newfound courage will prevent him from falling off a cliff or whatever. The Tomorrow War gives us hope! Dan may have not saved Colonel Forester of Romeo Command, but who knows what Muri’s brilliant scientific mind will come up with instead?
At the end of The Tomorrow War, Lieutenant Hart tells Dan that she thought kindly of his 2051 daughter saying, “It was an honor to have known her.” But had Hart survived the encounter in northern Russia, she could have met Muri all over again, even if she never joins the military. Something tells me Muri will have her hands full keeping the polar ice caps from melting even further and posing a much more domestic danger.