This man was a commander of skill and enterprise, and special circumstances enabled him by two brilliant offensive strokes to capture first Calais and afterwards Hulst.

Hulst was only taken after a severe struggle, in which De Rosne himself fell.
The special circumstances which favoured these operations were brought about by the conclusion of a treaty of alliance between France, England and the States.

This treaty was the result of prolonged negotiations; it was of short duration and its conditions were far from favourable to the United Provinces, but it was of great importance from the fact that for the first time the new-fledged republic was recognised by the neighbouring sovereigns of France and England as an independent state and was admitted into alliance on terms of equality.

It was, however, only with difficulty and through the insistence of Henry IV that Elizabeth was induced to acknowledge the independent status of the rebel provinces.

In return the republic was required to keep up a force of 8000 men for service in the Netherlands, and to despatch 4000 men to act with the French army in northern France--this auxiliary force to include the five English regiments in the States' service.