§ 333. Although a neutral is not required by his duty of impartiality to prohibit[631] the passage of belligerent men of-war through his maritime belt, or the temporary stay of such vessels in his ports, it is universally recognised that he must not allow admitted vessels to make the neutral maritime belt and neutral ports the base of their naval operations against the enemy. And article 5 of Convention XIII. enacts that "belligerents are forbidden to use neutral ports and waters as a base of naval operations against their adversaries." The following rules may be formulated as emanating from the principle:—
(1) A neutral must, so far as is in his power, prevent belligerent men-of-war from cruising within his portion of the maritime belt for the purpose of capturing enemy vessels as soon as they leave this belt. It must, however, be specially observed that a neutral is not required to prevent this beyond his power. It is absolutely impossible to prevent such cruising under all circumstances and conditions, especially in the case of neutrals who own possessions in distant parts of the globe. How many thousands of vessels would be necessary, if Great Britain, for instance, were unconditionally obliged to prevent such cruising in every portion of the maritime belt of all her numerous possessions scattered over all parts of the globe?
(2) A neutral must prevent a belligerent man-of-war from leaving a neutral port at the same time as an enemy man-of-war or an enemy merchantman, or must make other arrangements which prevent an attack so soon as both reach the Open Sea.[632] Article 16 of Convention XIII. enacts that there must be an interval of at least twenty-four hours between the departure of a belligerent warship and a ship of the other belligerent.
(3) A neutral must prevent a belligerent man-of-war, whose crew is reduced from any cause whatever, from enrolling sailors in his neutral ports, with the exception of such few hands as are necessary for the purpose of safely navigating the vessel to the nearest port of her home State.[633]
(4) A neutral must prevent belligerent men-of-war admitted to his ports or maritime belt from taking in such a quantity of provisions and coal as would enable them to continue their naval operations, for otherwise he would make it possible for them to cruise on the Open Sea near his maritime belt for the purpose of attacking enemy vessels.
There is, however, no unanimity of the Powers concerning the quantity of provisions and coal which belligerent men-of-war may be allowed to take in. Articles 19 and 20 of Convention XIII. of the Second Peace Conference enact the following:—
Article 19: "Belligerent war-ships may only revictual in neutral ports or roadsteads to bring up their supplies to the peace standard. Similarly these vessels may only ship sufficient fuel to enable them to reach the nearest port in their own country. They may, on the other hand, fill up their bunkers built to carry fuel, when in neutral countries which have adopted this method of determining the amount of fuel to be supplied. If in accordance with the law of the neutral Power, the ships are not supplied with coal within twenty-four hours of their arrival, the duration of their permitted stay is extended by twenty-four hours."
Article 20: "Belligerent war-ships which have shipped fuel in a port belonging to a neutral Power may not within the succeeding three months replenish their supply in a port of the same Power."
Great Britain, Japan, and Siam, while they have accepted article 20,[634] have entered a reservation against article 19. Great Britain upholds her rule that belligerent warships shall not be allowed to take in more provisions and fuel in neutral ports than is necessary to bring them safely to the nearest port of their own country.
While, therefore, the matter is not settled, it is agreed that it makes no difference whether the man-of-war concerned intends to buy provisions and coal on land or to take them in from transport vessels which accompany or meet her in neutral waters.