He met, however, with very partial success. His soldiers became entangled in bogs and morasses; they fell into ambuscades; they suffered every degree of privation and hardship for want of water and of food, and were continually entrapped by their enemies in situations where they had to fight in small numbers and at a great disadvantage. Then, too, the aged and feeble general was kept in a continual fever of anxiety and trouble by Bassianus, the son whom he had brought with him to the north. The dissoluteness and violence of his character were not changed by the change of scene. He formed plots and conspiracies against his father's authority; he raised mutinies in the army; he headed riots; and he was finally detected in a plan for actually assassinating his father. Severus, when he discovered this last enormity of wickedness, sent for his son to come to his imperial tent. He laid a naked sword before him, and then, after bitterly reproaching him with his undutiful and ungrateful conduct, he said, "If you wish to kill me, do it now. Here I stand, old, infirm, and helpless. You are young and strong, and can do it easily. I am ready. Strike the blow." Of course Bassianus shrunk from his father's reproaches, and went away without committing the crime to which he was thus reproachfully invited; but his character remained unchanged; and this constant trouble, added to all the other difficulties which Severus encountered, prevented his accomplishing his object of thoroughly conquering his northern foes. He made a sort of peace with them, and retiring south to the line of fortified posts which had been previously established, he determined to make it a fixed and certain boundary by building upon it a permanent wall. He put the whole force of his army upon the work, and in one or two years, as is said, he completed the structure. It is known in history as the Wall of Severus; and so solid, substantial, and permanent was the work, that the traces of it have not entirely disappeared to the present day.