I can point to the opinion of Justice Marshall in Brown v. US, "That war gives to the sovereign full right to take the persons and confiscate the property of the enemy wherever found, is conceded. The mitigations of this rigid rule, which the humane and wise policy of modern times has introduced into practice, will more or less affect the exercise of this right, but cannot impair the right itself. That remains undiminished, and when the sovereign authority shall chuse to bring it into operation, the judicial department must give effect to its will. But until that will shall be expressed, no power of condemnation can exist in the Court."
That will, which Marshall requires, came from the Congress in the form of the first and second Confiscation acts.
Based on the Supremacy Clause of the Constitution, any federal law in contrast to the powers defined in the Constitution is null and void (see Marbury v Madison). Amendment 5 states, "nor shall private property be taken for public use, without just compensation".
Again, the clause is not limited to time of peace, so Justice Marshall's opinion is moot. Again, perhaps you can enlighten as to specifically what clause of the Constitution grants the executive or military the power to seize private property without renumeration?
It's not a difficult question.