detailed, the over-running of Belgium; the other an eastern advance right up to the Rhine and to the town of Mayence. Both had failed. The failure in Belgium, culminating in the treason of Dumouriez, has been read. On the Rhine (where Mayence had been annexed by the French Parliament just as Belgium had been) the active hostility of the population and the gathering of the organised forces of the Allies had the same effect as had been produced in the Low Countries.
It was on March 21, 1793, that the Prussians crossed the Rhine at Bacharach, and within that week the French commander, Custine, began to fall back. On the first of April he was back again in French territory, leaving the garrison of Mayence, somewhat over twenty thousand men, to hold out as best it could; a fortnight later the Prussians had surrounded the town and the siege had begun.
On the north-eastern front, stretching from the Ardennes to the sea, a similar state of things was developing. There, a barrier of fortresses stood between the Allies and Paris, and a series of sieges corresponding to the siege of Mayence in the east had to be undertaken. At much the same time as the investment of Mayence, on April 9, the first step in this military task was taken by the Allies moving in between the fortress of Condé and the fortress of Valenciennes. Thenceforward it was the business of the Austrians under Coburg, with the Allies that were to reach him, to reduce the frontier fortresses
