Abu Mūsa (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "The death of my Ummah is by stabbing and the plague." It was said: "O Messenger of Allah, as for stabbing, we know it, but what is the plague?" He said: "Jabbing by your enemies from among the Jinn. In both cases, there are martyrs."
The Prophet (may Allah's peace and blessings be upon him) mentions that the death of the majority of the Muslims is caused by two things: First: fighting with weapons against the disbelievers in wars, and inter-Muslim fights at times of civil strife. Second: the plague, which causes widespread and collective death caused by the Muslims' enemies from among the non-Muslim Jinn, by jabbing them. Anyone who dies of either type, killing or the plague, is a martyr. However, some said that in this Hadīth, the Prophet (may Allah's peace and blessings be upon him) prayed that the members of his Ummah would die of either type so that they attain martyrdom. The first interpretation is the correct one. Allah knows best.