For compact, isometrically embedded Riemannian manifolds
N
↪
R
L
N \hookrightarrow \mathbb {R}^L
, we introduce a fourth-order version of the wave maps equation. By energy estimates, we prove an a priori estimate for smooth local solutions in the energy subcritical dimension
n
=
1
n = 1
,
2
2
. The estimate excludes blow-up of a Sobolev norm in finite existence times. In particular, combining this with recent work of local well-posedness of the Cauchy problem, it follows that for smooth initial data with compact support, there exists a (smooth) unique global solution in dimension
n
=
1
n=1
,
2
2
. We also give a proof of the uniqueness of solutions that are bounded in these Sobolev norms.