So let's talk about Battlefield 1's Operations—probably the closet approximation you will find to actual World War I combat in Battlefield 1. There are four operations in total, each featuring two maps, with one side on offense and the other side on defense. The offense's goal is to take two control points and push defenders back to the next line of defense, repeating the process until they either run out of attackers or the defenders run out of map. The defenders simply have to outlast them.
Operations might actually be my favorite mode in Battlefield 1. Moreso even than Conquest, it best captures the absolute chaos of World War I as tanks, planes, and stormtroopers try to overwhelm their opponent's defenses and take their control points. The defined roles also encourage a greater sense of teamwork, making it easier to launch concerted attacks, which stands in contrast to the sometimes piecemeal nature of Conquest.
Attackers have three waves of 150 soldiers apiece to try and take two maps worth of control points, which is no easy task when facing a determined and well-organized defense. Realizing this, Battlefield 1 deploys an airship to aid the attackers once the first wave goes down, complicating efforts to hunker down and hold each point. In return, defenders can launch planes and use anti-aircraft gun to try and take down the behemoth, though it requires a concerted attack to ultimately destroy.
Despite the presence of the airship, defenders seem to be at an advantage in the Operations. As they fall back, the fortifications at their disposal become more and more formidable, with one map even featuring a castle (as an aside, I love that Battlefield 1 has castles in it). That makes it comparatively easy for defenders to hold fast and fend off the waves of attackers, who have to work together to break through the concentrated enemy defenses.
It's for that reason that I think forcing the attackers to traverse two full maps is a mistake. In addition to requiring attackers to play almost perfectly to avoid running out of soldiers, it greatly draws out match times and makes the Operations mode less appealing overall. Granted, limiting the Operations to one map might swing the advantage to the attackers; but in my experience, when the attackers lose, it's usually in the first map and not the second. In any case, the Operations mode feels a bit bloated for its own good, which is too bad because the attack and defense dynamic works really well for Battlefield 1.
Another issue that worries me a bit is that the Operations may struggle to get enough players to make them worthwhile. I've had much better luck getting a game going in Conquest or Domination—familiar modes that reliably draw players of all skill levels. But when I try to go to Operations, I'm frequently confronted with long matchmaking times and dropped games. This will hopefully sort itself out when the full release hits, but early returns haven't been great. But with all that said, the Operations mode is a lot of fun, and I'm glad to see that Battlefield 1 is trying to be true to its subject matter.
Outside of the Operations, Battlefield 1 mostly moves across familiar territory. Domination is Conquest mode without vehicles, making it more akin to Call of Duty or any other competing shooter. Personally, I'm not a huge fan of Domination, mostly because it takes too much emphasis off Battlefield's key strengths, particularly its scope. That said, it does make for quicker matches, which some might find appealing.
Rush also makes a return; and again, while it's not my favorite mode in the world, it has its share of fans. In essence, Rush is a smaller-scale variant of Operations, with one side defending a pair of control points—in this case, telegraph stations—and the other side trying to blow them up. Like Domination, its smaller-scale makes for quicker games, which some may find appealing.
But in my humble opinion, Conquest continues to be where it's at. It does the most to differentiate Battlefield from its competitors, and it doesn't suffer from the balance issues of other modes. Along with Team Deathmatch, it will almost certainly continue to be the game's most popular mode. But even the Operations mode doesn't quite catch on, it's a noble experiment that plays to Battlefield 1's strengths. Hopefully it will be further refined over the course of additional DLC releases.