'Sailmaker' was a British and Canadian unrealised plan for General H. D. G. Crerar’s Canadian 1st Army to take the German-held island of Schouwen in the estuary of the Maas river in the south-western part of the German-occupied Netherlands (1944/45).
By November 1944 a number of special responsibilities had been allocated to each of the 1st Army’s corps. That entrusted to Lieutenant General J. T. Crocker’s British I Corps, which was holding the southern bank of the lower Maas river with Major General H. W. Foster’s (from 1 December Major General C. Vokes’s) Canadian 4th Armoured Division and Generał brygady Stanisław Maczek’s Polish 1st Armoured Divisions on the right and left respectively, was ordered to capture the large island of Schouwen to the north of the two Beveland islands.
Continued German occupation of Schouwen, which projects into the North Sea, was regarded as a threat to Allied shipping using the Scheldt river estuary to reach the port of Antwerp, and 'Sailmaker' was therefore conceived as the plan to seize Schouwen island and establish on it a radar station to provide warning of German air and/or naval attacks. Much work went into the development of the 'Sailmaker' plan, but senior Allied commanders ultimately concluded that the problems associated with the undertaking would be disproportionate to the possible results. There was a report that the German garrison on the island had been strengthened, and this indicated that at least one infantry brigade would be required for the attack. Complex arrangements would be necessary to create and control the bombing that would be required, and to provide the assault shipping which would be needed.
Finally some naval personnel expressed doubts about the very necessity for the operation, so on 20 November, on the recommendation of the 1st Army, 'Sailmaker' was postponed indefinitely, although it was reconsidered early in 1945.