The Republic could not let the capture of the Schenkenschans stand. Frederick Henry therefore concentrated a huge force to besiege the fortress even during the winter months of 1635. Spain held tenaciously on to the fortress and its strategic corridor through Cleves. She hoped that the pressure on this strategic point, and the threat of unhindered invasion of Gelderland and Utrecht, would force the Republic to give in. The planned Spanish invasion never materialised, however, as the stadtholder forced the surrender of the Spanish garrison in Schenkenschans in April 1636. This was a severe blow for Spain.