Why was the Battle of Tabuk called the 'Distressing Hour' (Al-Usrah)?

The expedition of Tabuk was named 'Usrah' (Hardship) because it occurred during a difficult time characterized by drought and scarcity of resources, in addition to the ripening of fruits and people's desire to remain in their shade. This made going out for war under those circumstances disliked and difficult for them, unlike the Prophet's usual practice of concealing his destination in other expeditions. However, due to the long distance and the severity of the situation, it was given that name.