The scenario discussed is not directly analogous, and obviously we shouldn't just read off from what prominent Marxists in history have said (coz they got plenty wrong, etc. etc.) but I found this essay by Trotsky quite illuminating.
"Let us assume that rebellion breaks out tomorrow in the French colony of Algeria under the banner of national independence and that the Italian government, motivated by its own imperialist interests, prepares to send weapons to the rebels. What should the attitude of the Italian workers be in this case? I have purposely taken an example of rebellion against a democratic imperialism with intervention on the side of the rebels from a fascist imperialism. Should the Italian workers prevent the shipping of arms to the Algerians? Let any ultra-leftists dare answer this question in the affirmative. Every revolutionist, together with the Italian workers and the rebellious Algerians, would spurn such an answer with indignation. Even if a general maritime strike broke out in fascist Italy at the same time, even in this case the strikers should make an exception in favor of those ships carrying aid to the colonial slaves in revolt; otherwise they would be no more than wretched trade unionists – not proletarian revolutionists.
At the same time, the French maritime workers, even though not faced with any strike whatsoever, would be compelled to exert every effort to block the shipment of ammunition intended for use against the rebels. Only such a policy on the part of the Italian and French workers constitutes the policy of revolutionary internationalism.
Does this not signify, however, that the Italian workers moderate their struggle in this case against the fascist regime? Not in the slightest. Fascism renders “aid” to the Algerians only in order to weaken its enemy, France, and to lay its rapacious hand on her colonies. The revolutionary Italian workers do not forget this for a single moment. They call upon the Algerians not to trust their treacherous “ally” and at the same time continue their own irreconcilable struggle against fascism, “the main enemy in their own country”. Only in this way can they gain the confidence of the rebels, help the rebellion and strengthen their own revolutionary position.
If the above is correct in peace-time, why does it become false in war-time? Everyone knows the postulate of the famous German military theoretician, Clausewitz, that war is the continuation of politics by other means. This profound thought leads naturally to the conclusion that the struggle against war is but the continuation of the general proletarian struggle during peace-time. Does the proletariat in peace-time reject and sabotage all the acts and measures of the bourgeois government?"
"An irreconcilable attitude against bourgeois militarism does not signify at all that the proletariat in all cases enters into a struggle against its own “national” army. At least the workers would not interfere with soldiers who are extinguishing a fire or rescuing drowning people during a flood; on the contrary, they would help side by side with the soldiers and fraternize with them. And the question is not exhausted merely by cases of elemental calamities. If the French fascists should make an attempt today at a coup d’etat and the Daladier government found itself forced to move troops against the fascists, the revolutionary workers, while maintaining their complete political independence, would fight against the fascists alongside of these troops. Thus in a number of cases the workers are forced not only to permit and tolerate, but actively to support the practical measures of the bourgeois government.
In ninety cases out of a hundred the workers actually place a minus sign where the bourgeoisie places a plus sign. In ten cases however they are forced to fix the same sign as the bourgeoisie but with their own seal, in which is expressed their mistrust of the bourgeoisie. The policy of the proletariat is not at all automatically derived from the policy of the bourgeoisie, bearing only the opposite sign – this would make every sectarian a master strategist; no, the revolutionary party must each time orient itself independently in the internal as well as the external situation, arriving at those decisions which correspond best to the interests of the proletariat. This rule applies just as much to the war period as to the period of peace."