  We theoretically study the decoherence and the dynamical decoupling control
of nitrogen-vacancy center electron spins in high-purity diamond, where the
hyperfine interaction with $^{13}$C nuclear spins is the dominating decoherence
mechanism. The decoherence is formulated as the entanglement between the
electron spin and the nuclear spins, which is induced by nuclear spin bath
evolution conditioned on the electron spin state. The nuclear spin bath
evolution is driven by elementary processes such as single spin precession and
pairwise flip-flops. The importance of different elementary processes in the
decoherence depends on the strength of the external magnetic field.
