Task: Question Understanding
Input (English): Passage: In the winter of 1666, the Dutch created a strong anti-English alliance. On 26 January, Louis declared war. In February, Frederick III of Denmark did the same after having received a large sum.  Then Brandenburg threatened to attack Münster from the east.  The promised English subsidies having remained largely hypothetical, Von Galen made peace with the Republic in April at Cleves. By the spring of 1666, the Dutch had rebuilt their fleet with much heavier ships — thirty of them possessing more cannon than any Dutch ship in early 1665 — and threatened to join with the French.:71 Charles made a new peace offer in February, employing a French nobleman in Orange service, Henri Buat, as messenger. In it, he vaguely promised to moderate his demands if the Dutch would only appoint William in some responsible function and pay £200,000 in "indemnities". De Witt considered it a mere feint to create dissension among the Dutch and between them and France. A new confrontation was inevitable.
Question: In which year did the Dutch have their most impressive ships?
Output (English): date