Opslag surrendered on the 7th July. He then moved to the west of
Groningen, and attacked the forts of Yementil and Lettebaest, which fell
into his hands on the 11th July. He then moved along the Nyenoort
through the Seven Wolds and Drenthe to Steenwyk, before which strongly
fortified city he arrived on the 15th July.

Meantime, he received intercepted letters from Verdugo to the Duke of
Parma, dated 19th June from Groningen. In these, the Spanish stadholder
informed Farnese that the enemy was hovering about his neighbourhood, and
that it would be necessary for the duke to take the field in person in
considerable force, or that Groningen would be lost, and with it the
Spanish forces in the province. He enclosed a memorial of the course
proper to be adopted by the duke for his relief.

Notwithstanding the strictness by which Philip had tied his great
general's hands, Farnese felt the urgency of the situation. By the end
of June, accordingly, although full of his measures for marching to the
relief of the Leaguers in Normandy, he moved into Gelderland, coming by
way of Xanten, Rees, and neighbouring places. Here he paused for a
moment perplexed, doubting whether to take the aggressive in Gelderland
or to march straight to the relief of Groningen. He decided that it was
better for the moment to protect the line of the Waal. Shipping his army
accordingly into the Batavian Island or Good-meadow (Bet-uwe), which lies
between the two great horns of the Rhine, he laid siege to Fort
Knodsenburg, which Maurice had built the year before, on the right bank
of the Waal for the purpose of attacking Nymegen. Farnese, knowing that
the general of the States was occupied with his whole army far away to
the north, and separated from him by two great rivers, wide and deep, and
by the whole breadth of that dangerous district called the Foul-meadow
(Vel-uwe), and by the vast quagmire known as the Rouvenian morass, which