This may be kinda cliche and a lot of this will be assumptions and intuition but please bear with me.
Ironwood is not only a headmaster from Atlas but also the general of the army there. Ozpin makes a point of saying that it is very unusual for a headmaster to travel with their students to the Vytal Festival. This can be assumed to leave his school in the hands of a deputy headmaster/headmistress which would be unlikely as they traditionally take great pride in their schools. While he says that the reason he brought the army with him was for caution, he seemed somewhat vague. Also, he has been seen in the trailer to create new robots (and I think Penny).
Cinder, Emerald, and Mercury have infiltrated Beacon under the guise of coming from Atlas. Obviously there would be some amount of paperwork that would have to be completed for anyone to even get a dorm at the school if they are from a different school. Also, stated in the first episode, they were moving onto stage two, and no longer needed dust.
The mech that is seen in the trailer is pretty badass to say the least. It also bears some color resemblance (white or silver) to the robots that are displayed by Ironwood to the people of Vale. The mech is also pretty damn big and seems to carry some pretty severe weaponry. Possibly the weaponry is not homemade by the White Fang, but stolen for the mech or even given to them. I assume this much because I highly doubt the White Fang (being segregated and abused) may not have the expertise for the completion of such a beast. Any faunus that would have talent in building mechs of that magnitude and caliber may already have been hired by humans to assist them, or could have a conscious and not want to be affiliated with the White Fang. Most of this is heavy assumption so I may be wrong.
My theory is that Ironwood is Cinder's in at Beacon. Granted no one has seen her face from Beacon but Ruby seemed a little off-put by the eyes. Ironwood also seemed to be in Vale before the end of the last season as it is him who has picked up Penny from the docks (but apart from a possible tracker how did he know she was there). Ironwood is also the general of an army and possibly an entrepreneur who make robots. This would allow him to advanced military tech to be used for his own purposes, e.g. giving it to Cinder and Roman to use in the White Fang. Also note that Cinder's excuse for being at Beacon is that they are from Atlas, which would need to have some amount of merit to pass an inquiry should Ruby or anyone else ask about them. This would again lead back to Ironwood and his power to cover them should anything arise.
Mech time. As stated before, the White Fang mech bears a little bit of a resemblance to Ironwood's robot guardians. If you would remember from episode one of Volume one, when Roman and his thugs attempt to rob From Dust til Dawn, when they demand the Dust crystals they say something about fire. Being that fire is red or orange depending on color, the robot guards all bear a red glow under the plating. This is seen in the Black trailer when Adam and Blake are attacking the Schnee train. Then in the trailer, the robots Ironwood displays, have the same red glow though seen very briefly. My thoughts are that the robots run on Dust (pry not surprising) and the mech does too, red Dust giving the mech the amount of fire power it does while also acting as a sort of combustion engine of some kind. Also, though it may make sense where he is, why would Ironwood decide to unveil the new advanced robots in Vale though his home and the base of his army is in Atlas.
Army. A possible explanation to why Ironwood brought his army was to operate on the side of the White Fang. I think that this is not necessarily an army of a certain nation, but in essence a PMC specifically Ironwood's. This would eliminate the concept of the army fighting for the innocent of Vale, replacing that with the promise of a paycheck which would come from Dust that can be sold very expensively after Roman's operations have stolen so much and driven up the price. Even if the army was made up of robots instead of humans and faunus, they could be programmed to follow orders from certain individuals alone like Cinder or Ironwood, allowing them to not have any account of what they are fighting with only the commands to attack. In reference to episode two and the opening credits, Cinder can be seen lounging on what I assume to be the grounds of Beacon as several airships pass over head, which are similar to the airships seen at the beginning of episode two, and assumed to be there because of Ironwood. Even Ozpin states that to show such a force during a time of peace is unwise, also saying they must be tactful in what they are doing.
Okay, since you are this far into this I would like to thank you first off. Secondly, a lot of this may ring a bell with Project Freelancer having serious weaponry and technology and turning out to use it for evil or for sadistic fun. I would not be surprised with this kind of parallel because everyone who has produced/directed/written shows, movies, games and such likes to draw off of past experience. This is evident with easter eggs (Puma), character similarities (Ruby and Carolina both have red hair and extreme speed) and other similar things.
This concept basically popped into my head after watching the episode and it just seemed to fit together a little too well. If you think I missed anything please leave a comment. Same goes if you think I got something wrong and would like to state your own opinion. If you have any other theories that you have developed or you think bear some amount of merit please post them. Also, please share with your friends so that we can get some feedback and develop this or other theories more.