The French had planned for a defensive war and built tanks accordingly. Their infantry tanks were heavily armoured. But, also, generally, they were relatively sluggish, and operationally in terms of control of their forces, the French were at a disadvantage and were outmaneuvered by the German forces. When the French were able to mount an attack their tanks could be very effective. On 16 May, during the Battle of France a single Char B1 heavy tank, the "Eure", attacked and destroyed thirteen German tanks lying in ambush in Stonne, all of them Panzer IIIs and Panzer IVs, in the course of a few minutes. The tank safely returned despite being hit 140 times (this event is not verifiable in German documents and relies on the statements of the crew). In his book "Panzer Leader", Heinz Guderian wrote of a tank battle south of Juniville: