'Ordnance' was a British naval evacuation of Royal Marines, British army forces and Dutch personnel from the Hoek van Holland in the Netherlands as the German forces approached in 'Gelb' (13 May 1940).

The undertaking was schemed within a British plan to deny the Germans the use of the main Dutch ports (IJmuiden, Hoek van Holland, Antwerp, Vlissingen and Zeebrugge) with their excellent facilities in the event that the defeat of the Netherlands appeared imminent. The demolitions at the four principal ports were, therefore, planned at Dover by Vice Admiral B. H. Ramsay according to orders dated 7 May. One destroyer was to take a single demolition team to each destination, while military parties were also embarked for IJmuiden, the Hoek van Holland and Antwerp to ensure that the very large oil stocks in or near those ports were destroyed. The blocking of Ostend and Zeebrugge, the importance of which lay in the fact that they were the terminal points of canal systems running into the heart of industrial Germany, had already been planned in the Admiralty, and the orders had been issued early in October 1939.

On 10 May, the start of 'Gelb' occasioned the departure from Dover of four destroyers with the demolition parties, the sailing of Princess Victoria and the ships of the 20^th Minelaying Flotilla to lay a defensive minefield off the Dutch coast, and the movement of the ships of Rear Admiral G. F. B. Edward-Collins’s 2^nd Cruiser Squadron to IJmuiden to bring back the Dutch gold reserves and clear the port of merchant shipping. At the same time blockships were readied for departure, and reinforcements of flotilla vessels were ordered to the Nore and Dover commands.

On 11 May the light cruiser Arethusa and two destroyers escorted back a pair of merchant vessels carrying the Dutch bullion and, on 12 May, the destroyer Codrington embarked Princess Juliana, the crown princess, and her family at IJmuiden and brought them to England.

The demolition and blocking of that port were started on 14 May and successfully completed with the aid of the local Dutch forces. The military party which had been sent to Amsterdam to destroy the large oil reserves at first encountered difficulties from the Dutch but, finally, fired all the reserves. The British parties in fact faced problems with the with the Dutch local authorities in several places, for it was perhaps inevitable that the owners of valuable property should resent any attempt at the destruction of their property. In the Low Countries resentment of this nature prevented the demolitions at Flushing, but those at the Hoek van Holland and Antwerp were completed: similar difficulties were later encountered in French ports.

The party sent to the Hoek van Holland included a military section ordered to destroy the oil reserves at Rotterdam, but its task was obstructed at the first attempt even though a considerable part of the city was already in German hands, and it was not until the afternoon of 13 May that the tanks set on fire.

To secure the safety of the British demolition parties a Royal Marine guard was hastily sent across in two destroyers on the night of 11/12 May, and followed by a composite battalion of Irish and Welsh Guards during the next night. The destroyer leader Malcolm of the 16^th Destroyer Flotilla arrived at the Hoek van Holland early on 13 May and took charge of the evacuations. At 12.00 Queen Wilhelmina and her party arrived and were taken on board the destroyer Hereward for transport to Harwich. During the evening of the same day the Dutch government and Allied embassy staffs embarked for England in the destroyer Windsor. By the following day it had become clear that Dutch resistance was close to an end, so the British government ordered the Guards and Marines to be brought back. The destroyers Boreas, Brilliant, Keith, Verity, Wivern and Wolsey were despatched from Dover to transport and protect the troops, and were later joined by another pair of destroyers, Westminster and Whitley, off the Hoek van Holland, and on the afternoon of 14 May, after being delayed by fog, the evacuation was successfully accomplished.

Even at this late stage in the defeat of the Netherlands, there were still many Dutch who obstructed the demolition work and the blocking of the harbour, as a result of which neither task was completed.

The last British ships sailed at 20.00, just before the Germans entered the town. Offers to embark Dutch troops were refused and a plan to lift numbers of Dutch troops with destroyers from the Hoek van Holland, IJmuiden, Scheveningen and Texel was abandoned.

At Flushing better success attended the naval demolition party, and 16 merchant vessels departed for England on 11 May. The pressure of German air operations, involving bombing and the laying of magnetic mines, increased steadily, however, and the British destroyers were in action continuously and suffering increasing damage. On 12 May some air cover was afforded by Bristol Blenheim twin-engined heavy fighters and Hawker Hurricane single-engined fighters operating from England, but the former were too slow to intercept the German dive-bombers and the latter’s short endurance limited their patrols to periods of about 30 minutes.

On 14 May the Dutch government informed the British government that it was planning to surrender its forces on the mainland, but to continue resistance on the island of Walcheren with the aid of French forces. On the next day the German bombing was heavier, the destroyer Winchester was damaged and Valentine was lost while trying to protect one of the Scheldt river ferries.

On 16 May the Germans' advance forced back the French troops, and the passage of the retreating Allied soldiers through Flushing hampered the work of the demolition parties. Some damage was done, but German reports reveal that the harbour was again open to shipping by 5 June.

Finally, during the evening of 17 May, three days after all the other Dutch ports had been evacuated, the British party crossed the Scheldt river to the west and continued to Dunkirk by road.