Bridges into Washington.The sentry and vedette guarding the approach to Washington suggest one reason why Early did not make his approach to the capital from the Virginia side of the Potomac. A chain of more than twenty forts protected the roads to Long Bridge (shown below), and there was no way of marching troops into the city from the south, excepting over such exposed passages. Most of the troops left for the defense of the city were on the Virginia side. Therefore Early wisely picked out the northern outposts as the more vulnerable. Long Bridge was closely guarded at all times, like Chain Bridge and the other approaches, and at night the planks of its floor were removed.