Most of the action from this trailer has appeared in the previous trailer (see "'Transformers: Age of Extinction' Trailer").  But at 1:24, there are some better glimpses of the unknown enemies menacing Earth.  Optimus Prime then intones, "This is not war, it’s human extinction," followed by some new city action sequences.
 
The big payoff though, comes at 2:11, with Prime stating "We need a new army," which is followed by a shot of a fire-breathing Grimlock, culminating in Prime riding the city-stomping dinobot into battle.