The people of this province had taken no part in the attack of Mason and Brent, but the Susquehannocks were not in the humor to make nice distinctions. In seeking revenge for the murder of their braves they held all whites equally guilty, and fell immediately upon the nearest plantations. Thus were the Marylanders made to suffer for the rashness of the Virginia frontiersmen. Feeling that it was his duty to aid the neighboring province in this war brought on by the hasty action of two of his own officers, and fearing that depredations upon the Virginia frontiers could not long be prevented, Sir William Berkeley decided to join Governor Calvert in a vigorous attack upon the savages. Colonel John Washington, great-grandfather of George Washington, at the head of several hundred men, was despatched across the Potomac to effect a junction with the Maryland troops.[482] The combined forces of the two colonies are said to have numbered "neer a thousand men".[483] Unable to withstand this army in the open field, the Indians fell back upon a fort which they had erected upon the north bank of the Potomac, and here awaited the approach of the English. Their fortress had been constructed with such care and skill that the white men were unable to carry it by storm. The outer works consisted of lines of tree trunks, from five to eight inches in diameter, "watled 6 inches apart to shoot through", their tops firmly twisted together. Behind this was a ditch, and within all a square citadel, with high walls and "fflankers having many loop-holes". The fire of the red-skins from behind these works proved so deadly that hopes of a successful assault had to be abandoned. Nor could breaches be effected, for the allies were not provided with heavy guns. The moist and swampy ground surrounding the fort made it impossible to approach by means of trenches.[484]