The stochastic duel models between two forces that on one side all members have ability to attack and on the other side some members do not have the ability to attack are established. Under the condition of stochastic aiming, the differential equations of state probability of the grouped and not grouped offensive side are established. Under the different combat termination decision rules, the algorithms for the probability of wining of the grouped and not grouped offensive side, the probability of successful defense of defense side and the probability of the draw of two side based on recursive formulae are given. In the cases that offensive side grouped, the properties of the probability of winning are proved under the conditions of different combat termination decision rules. Different combat termination decision rules result in a very different property of probability of winning of offensive side. Through the concrete numerical example probabilities of winning with different parameters of the grouped and not grouped offensive side are compared. The results show that there is not a attack scenario which is the absolute dominant.