Complex sentence: Spain itself had no timber suitable for building ships and its unfriendly relations with northern Europe made drawing supplies from that source impossible; consequently it obtained timber from San Domingo, Cuba and Jamaica for building many ships of the Spanish Armada prior to 1588.
Split into simpler sentences: Spain itself had no timber suitable for building ships and her unfriendly relations with northern Europe made it impossible to draw supplies from that source. The natural conclusion is that Spain obtained timber from San Domingo, Cuba and Jamaica for building many ships of the Spanish Armada prior to 1588.