I wonder. I was building some privateers, frigates and ship of the lines (sp?) as I suspected Alex was headed our way. My thought was to sink whatever I could before he reached me with my privateers. I also blocked land access with the frig/sotl's as he had astronomy but not chemistry so if he invaded it woul dbe with galleons only.
It was an interesting choice really to select a save where we knew Alex was in war mode. Yet you still made the mark. Then again the risk was always low I guess as he was backwards.