After this, Mohammed did not scruple to employ the system of warfare by assassination, if warfare it can be called. Some tribes, emboldened by the report of the Meccan success, began to treat Moslem emissaries with scant courtesy, and went so far as to murder some. Mohammed retaliated by sending men to balance the scales in the same criminal way, particularly in treating with the Jews. An idea had grown up in his mind that these people had determined to murder him. This, with matters of minor importance, already referred to, at last led to an organised attempt to subjugate them. A large, influential tribe was besieged; their date trees, lands, and property wantonly destroyed. Eventually the whole tribe surrendered, and were glad to march away with what possessions their camels could carry. This led to a combination of other Jewish tribes, which laid siege to Medinah. The siege was not successful, and barbarous treatment was meted out to the besiegers. After much skirmishing and general fighting, a number of the Jews who had been captured were decapitated, while their women and children were enslaved. Those who were unwilling to embrace Islam, were compelled to pay tribute. So the prosperity and success of Islam was assured. The Jews were no longer bold enough to cause the prophet any anxiety as to the validity of his prophetic claims, nor were they of a mind that would arouse fear as to their fighting abilities. They were true descendants of Isaac and Jacob, who were both men of peace, and were not qualified for success in war against the posterity of the active warlike Ishmael and Esau. Freed from all anxiety in this direction, the prophet, realising that the security of Medinah could never be assured while the Meccans were opposed to him, began to formulate plans for the conquest of their city. His first step was to try and conciliate them, with a view to sending a pilgrim band into the city, but the citizens were far too cautious and suspicious to allow that. At last, however, they were prevailed upon to receive his son-in-law, Omar, who succeeded in persuading a section of the Meccans of the injustice of barring the Holy Temple to those who, although their enemies, were, after all, their kinsmen. This led to a treaty, in which Mohammed brought shame upon his followers because of his concessions. The arrangements were that for ten years, peace between the prophet and the Meccans should be maintained, and that within a year a party of the Moslems were to be allowed to make a pilgrimage to the Kaaba.