When Oxenstiern and Richelieu conferred alone together, the two ministers had recourse to Latin, that common tongue of the cultivated minds of their time, and nobody was present at their conversation.
Oxenstiern soon departed for Holland, laden with attentions and presents: he carried away with him a new treaty of alliance between Sweden and France, and the assurance that the king was about to declare war against Spain.
And it broke out, accordingly, on the 19th of May, 1635.

The violation of the electorate of Treves by the Cardinal Infante, and the carrying-off of the elector-archbishop served as pretext; and Louis XIII.

declared himself protector of a feeble prince who had placed in his hands the custody of several places.

Alencon, herald-at-arms of France, appeared at Brussels, proclamation of war in hand; and, not be able to obtain an interview with the Cardinal Infante, he hurled it at the feet of the Belgian herald-at-arms commissioned to receive him, and he affixed a copy of it to a post he set up in the ground in the last Flemish village, near the frontier.

On the 6th of June, a proclamation of the king's summoned the Spanish Low Countries to revolt.