Complex sentence: The ships from Brest had deliberately departed before they were fully supplied, to avoid the possibility of being blockaded by the British, so serious problems arose as the wait dragged out to several weeks, no arrangements having been made to take on additional supplies in Spain.
Split into simpler sentences: The ships from Brest had deliberately departed before they were fully supplied, to avoid the possibility of being blockaded by the British. Serious problems consequently arose as the wait dragged out to several weeks, and no arrangements were made to take on additional supplies in Spain.