The eminent Muslim scholar and renowned Da`iyah, Sheikh `Abdel Khaliq Hasan Ash-Shareef, states:
“Dar Al-Kufr and Dar Al-Harb are not synonymous. Dar Al-Kufr (abode of disbelief) is the abode where the residents are non-Muslims and people in authority of that place are non-Muslims.
As for Dar Al-Harb or the abode of war, it is one of the categories of Dar Al-Kufr. It is the abode where its residents are in a state of war and declaring war against Muslims.
It goes without saying that we may have a peace treaty or truce or the like between Muslims and the abode of Kufr. So, definitely Dar Al-Kufr and Dar Al-Harb are not synonymous.”