Surrey was not to be deceived, and steadily refused to prophesy smooth things. He believed that Ireland could only be reduced by conquest, and that the easiest method was to master one district at a time, gradually pushing forward the frontier until the whole country was obedient. A permanent army of 500 men might perhaps effect this, while at least 6,000 would be required for a rapid conquest. Edward I. had taken ten years to subdue Wales, and that great king had given almost constant personal attention to the work. Yet Wales was unprotected by the sea, and was not a fifth part the size of Ireland. All artillery and munitions of war would have to be brought from England, and fortresses must be built to bridle each tract of country successively occupied. Nor could a military occupation endure unless accompanied by a large plan of colonisation. Thus only could the natives be brought to labour and settled order. We can see, though Henry VIII. could not, how justly Surrey estimated the magnitude of England's task in Ireland.[89] [Sidenote: Activity of Surrey.] In July 1521 the Irish bordering on the Pale took their usual advantage of the season. O'Connor, O'More, and O'Carroll, the latter all unmindful of his last year's oath and of more recent promises, collected a great host and prepared to attack the Pale. Surrey, who had lately prorogued his Parliament after a ten days' session, was in Dublin, and by his promptitude averted the danger. O'Connor's castle, near Edenderry, was soon in his hands, being unable to resist the fire of three pieces of heavy ordnance for a single day. It became an axiom in Irish warfare that the Government could always make its way with artillery. Surrey proposed to hold O'Connor's stronghold permanently, and to use it against the Irishry as Berwick was used against the Scots. He destroyed all the corn far and wide, the people with their cattle flying before him, while Sir Piers Butler played the like part in Ely O'Carroll. The vigour shown by the Lord-Lieutenant had the effect which vigour generally has in Ireland, and the confederacy gave him little further trouble. Meanwhile, the North was in a blaze. O'Donnell professed loyalty, but was not trusted by Surrey, who, however, thought it wise to humour him. O'Neill was willing to be on good terms with the Government, and was on his way to Dundalk accompanied by Magennis and a large force, when the O'Donnells attacked him in the rear. Fifteen hundred cows were driven off and seventeen of the Magennis' villages burned, so that the allies were forced to retrace their steps. The chief of Tyrconnell feared that if his great neighbour were once at peace with the Pale he would be too strong for him in the everlasting private war of Northern Ulster.[90] [Sidenote: Uncertainty of English policy.]