2-And the surplus amount paid to a warring Kafir by a Muslim for the borrowed loan is Interest or no?
الجواب حامدا و مصلیا
In the name of Allah, the Most Beneficent and the Most Merciful
According to the decisive decree, it is not allowed in Shari’a for a Muslim with a Kafir or a Kafir with a Muslim, to engage in Interest based transactions, neither in an Islamic territory nor in a Kufr territory or in a territory of War. The situation mentioned here is fallen in the similar category. Hence it is necessary to avoid and refrain from engaging in the aforesaid transaction.
Allah knows best.