Is he who dies unawares, such as one killed from behind, or one upon whom explosives fall without his being able to defend himself, considered a martyr, similar to one who dies defending himself?

Any Muslim who is unjustly killed receives the reward of a martyr in the hereafter, and is washed and prayed over in this world. It is not a condition for one who is unjustly killed to confront the aggressors in order to attain the reward of martyrs. As for our brothers in Gaza whose homes have been destroyed, they are martyrs because they were killed unjustly, and the Prophet, peace and blessings be upon him, said: "The one who dies under a collapsed building is a martyr," and because they were killed at the hands of warring disbelievers.