  The algebraic unknotting number u_a(K) of a knot K was introduced by Hitoshi
Murakami. It equals the minimal number of crossing changes needed to turn K
into an Alexander polynomial one knot. In a previous paper the authors used the
Blanchfield form of a knot K to define an invariant n(K) and proved that n(K)
is a lower bound on u_a(K). They also showed that n(K) subsumes all previous
classical lower bounds on the (algebraic) unknotting number. In this paper we
prove that n(K)=u_a(K).
