You can break your lease without penalty if you're in the military and being transferred.
Otherwise, you need to look at your lease and see what, if any, provisions it includes for early termination. If you're lucky, the landlord may let you move if you forfeit your security deposit.
Offer to help the landlord find a new tenant (and expect to pay his expenses for doing so). You'll be responsible for the rent until the landlord finds the tenant, and while he has to make a good faith effort to do so, he doesn't have to accept just anyone so you can stop paying rent on two places.