So Why is Ares/Sir Patrick Pushing For Peace?
Despite the true identity of 'Sir Patrick' being spoiled after test screenings, the role his character plays in the story is likely to throw viewers off the trail. On the surface, it makes far more sense for Ares to be desperately fighting to keep the war alive than to be the one pushing to end it. In fact, some audience members may have a hard time actually grasping Ares's angle here, provided you miss one or two lines of dialogue. Yes, Sir Patrick is the one arguing for an armistice with Germany... knowing that Ludendorff and Maru were already determined to launch their attack.
For some historical context, World War I didn't actually end in a "defeat" like World War II. That armistice Sir Patrick was pushing for was actually what ceased hostilities in the conflict, with both sides agreeing to a truce, allowing all parties to return to their own borders (many of which were changed in the same agreement). The point is that Germany was, as the movie shows, facing difficulties if the fight continued. And while Ludendorff (the fictional version) was fighting for bloodshed and slaughter, Germany had been fighting for empire. Their window had closed, but Ludendorff's was still open.
That's what Ares was counting on, knowing that if a ceasefire could be reached due to all parties' growing horror with what The Great War was causing, and then broken, they would have no choice but to keep sliding down into total annihilation. Thankfully, his efforts for peace succeeded... but his other plan was thwarted.
Wouldn't Steve Have Spread The Toxic Gas?
As Diana takes her chances against Ares in open, godly combat, Steve Trevor takes to the skies aboard the plane programmed to detonate in London, England, covering the population in the deadly mustard gas designed by Doctor Poison. Knowing that the timers on the weapons have determined that they will be deployed, Steve's only chance to save the day is to get behind the controls, ensure that the plane reaches an altitude far enough away from his allies to protect them, and detonate the plane's payload.
Thanks to the frequent use of gas attacks and chemical dispersion in science fiction and blockbuster films, some in the audience might ask: "isn't it a BAD idea to fly killer chemical weapons up into the sky, and then scatter them into the wind over a larger area?" It's a fair point to raise, especially if you're concerned for those living in the nearby countryside. However, the characters point out that the chemical is hydrogen-based instead of the usual sulfur, meaning it's as combustible as it is deadly.
So when ignited by a bullet (in typical movie chemical reaction fashion) the chemical compound will rapidly burn, creating a massive explosion while destroying itself before it can harm a soul.
How Can Diana Kill Ares When Zeus Couldn't?
During Ares's monologue late in the film, the villain is shown recovering from his wounds inflicted by his father, Zeus. The question then becomes: if Zeus wasn't actually able to kill Ares - easy to believe, since he is the God of War, and therefore able to kill the other gods - then how can Diana, who is merely a demigod? The answer may not be obvious or offered directly, but it's worth reminding people that the "power" of Greek gods shouldn't be thought of as being 'watered-down' through generations. Zeus was a god and Hippolyta wasn't, sure... but she is immortal, and created by Zeus to be something special, not to mention the most fearsome of her entire race of fearsome and powerful warriors.
The easiest explanation would be that Zeus simply couldn't kill Ares because he was his son (and the connection between family is a pretty strong theme in the film). The missing ingredient here, as we see it, is the conviction behind Diana's powers and ultimate attack. In the original showdown, Zeus was in denial claiming men were good and Ares was bad. Ares denied his manipulation, claiming men were bad, and he was right. Diana is unlike either: she knows men are imperfect, but fights for the belief they can be better... a belief that, thanks to Steve, is rooted in love.
Perhaps that was the missing ingredient needed to truly overpower the embodiment and mentality of War?
If Ares is Dead, Why Did Wars Continue?
Once Diana manages to slay the man she believes to be Ares, she naively assumes that the people involved in the war will simply stop fighting, having absolutely no natural inclination towards hate, violence, or lust for power. But as they keep rolling forward, she is utterly disillusioned. She has learned what the audience knows: people are all too ready to hate, kill, and claim... no extra encouragement. In that moment, she seems to have reached the point she refers to in Batman V Superman, having "turned her back" from the horrors of man's world, only now realizing that Ares wasn't needed to plunge the world into "a century of horrors."
Until she kills the actual Ares, and everyone puts down their weapons, and agrees to end the war. It could be seen as actually validating Diana's naivete, and the audience may have trouble accepting the implied message, knowing that war was by no means over. The best answer we can come up with is that Diana succeeded in stopping Ares's specific plan - but by that point, as we mentioned before, humanity had already acquired the kinds of weapons they never should have, without evolving their basic nature or value of life and conflict.
Ares got humanity to the 20th Century, and it was too hard a ball to stop rolling. That being said director Patty Jenkins explained Wonder Woman's link to BvS, clarifying that Diana "turning away" may simply mean she stopped trying to save the world from itself in some grand sense. Not alone, anyway...
- Wonder Woman (2017) release date: Jun 02, 2017