Contemporary English sources typically refer to him as Admiral Opdam or Lord Obdam because it was not until 1657 that he bought the Wassenaar Estate from relatives and thus acquired its title.

[2] Because his father had been Lieutenant-Admiral, and through the influence of de Witt, he was made "Delegate of the States to the National Fleet", thereby becoming responsible for all day-to-day dealings between the States-General and the navy, a position that carried much power.

[4] Near the end of the war, in the Battle of Scheveningen, the supreme commander of the confederate Dutch fleet, Lieutenant-Admiral Maarten Tromp, was killed in action.

His second in command had been Vice-Admiral Witte de With, both a courageous and competent sailor and a man seen as politically reliable as he was not a supporter of the Orangist faction.

The first candidate to be approached, Louis of Nassau-Beverweerd, an illegitimate son of Maurice, Prince of Orange and experienced military commander who had agreed to cooperate with the republican administration of Johan de Witt and the regents of the Dutch cities, becoming First Noble of Holland, declined but recommended his fellow noble, van Wassenaer.

[11] Van Wassenaer at first refused, then made his acceptance conditional on his appointment as full Admiral, a post normally reserved for a Prince of Orange, not merely Lieutenant-Admiral.

[12] In 1654, the Dutch Navy found a new commander in Jacob van Wassenaer Obdam, Lieutenant-Admiral of Holland and West Frisia.

[14] Although de Witt had convinced the States General to spend four million guilders in agreeing to building sixty new warships to augment the existing fleet in the First Anglo-Dutch War, including several comparable to the all but the largest English ships and much heavier than the average existing Dutch warship, many were relatively small convoy escorts, little more than frigates by English standards, and not all those planned had been completed or fitted out by 1665.

[16] Before the Anglo-Dutch wars, the typical solution when fighting Spanish galleons had always been the direct attack having the weather gauge, using superior maneuverability and numbers, or if that failed: employing fireships and boarding.

Robert Blake created a very formal version that worked even better for the English as they had powerful ships and a more professional navy, while the Dutch employed many armed merchants.

Sailing in a battle line in a defensive leeward position, the wind, blowing from the side of the enemy, would give the guns of the Dutch ships a higher elevation and therefore a better range.

Also, the Republic was critically dependent on Scandinavian wood to build ships and Polish grain to feed its large urban population.

Van Wassenaer and most of the Dutch fleet left Danish waters in late October once this task had been almost completed, leaving De Ruyter with a small squadron until the terms peace was agreed.

[27] The First and Second Anglo-Dutch wars arose from a combination of commercial and maritime rivalry religious and political differences between England and the Netherlands (the Third Anglo-Dutch War, however, was less consequent upon commercial rivalry:[28] while Oliver Cromwell wished to prevent any member of the House of Orange becoming stadtholder or holding any other public office in the Netherlands; whereas following the Stuart Restoration, Charles II of England tried to promote his nephew William as a possible stadtholder.[29]).

Although the Second Anglo-Dutch War resulted from long-standing commercial tensions between England and the Netherlands that had escalated from 1664, following English provocations in North America and West Africa,[30] diplomatic negotiations to avoid the outbreak of war failed, largely because a group of ambitious English politicians and naval officers frustrated these efforts to reach any accommodation between the two parties.

The Grand Pensionary and leading Dutch politician, Johan de Witt and other members of the States-General, formed a commission to supervise Obdam,[34] and gave him detailed instructions comprising 26 articles, ordering to attack the English aggressively when and where he could do them most damage.

[35][36] The same instructions issued by the commission headed by de Witt insisted on specifying that the Dutch fleet's order of battle should involve its division into a seven squadrons with a total of 21 flag officers for political reasons.

[citation needed] Realising his fleet was still too inferior in organisation, training, discipline and firepower to challenge the English successfully in a decisive battle, van Wassenaer was prepared only to seek a limited confrontation with his fleet in a defensive leeward position from which it could disengage quickly and return to its ports without openly disobeying orders.

[42] He has been accused of lack both of leadership and tactical insight, and it is claimed he had only succeeded in earlier battles when Egbert Bartholomeusz Kortenaer was his flag captain.

[43] However, Obdam's tactical decisions may relate to his appreciation that his out-gunned and poorly organised fleet could only succeed in battle under ideal conditions, and it needed to be able to disengage if it risked defeat.

[47] The loss of the flagship and death of van Wassenaer, just as the English Blue and White squadrons were attacking, seriously affected Dutch morale, further damaged by the uncertainty over his successor.

"[citation needed] Like any Dutch Admiral killed in action Jacob van Wassenaer Obdam was given a marble grave memorial, in this case, of course, a cenotaph.