  The electronic energy of $\mathrm H_2^+$ in magnetic fields of up to
$B=0.2B_0$ (or 4.7 $\times 10^4$ Tesla) is investigated. Numerical values of
the magnetic susceptibility for both the diamagnetic and paramagnetic
contributions are reported for arbitrary orientations of the molecule in the
magnetic field. It is shown that both diamagnetic and paramagnetic
susceptibilities grow with inclination, while paramagnetic susceptibility is
systematically much smaller than the diamagnetic one. Accurate two-dimensional
Born-Oppenheimer surfaces are obtained with special trial functions. Using
these surfaces, vibrational and rotational states are computed and analysed for
the isotopologues $\mathrm H_2^+$ and $\mathrm D_2^+$.
