The battle of Karbala (10th Muharram 61AH) was when the Prophet beloved grandson, the leader of the youth of paradise, Imam Hussain (as), was martyred in the name of Islam and the truth.
In the scorching sun in the desert of modern day Iraq, Imam Hussain (as) army outnumbered by Yazid's military and also very thirsty as the opposition had blocked them from the water. Yet they continued fighting until their lives were taken in the name of Islam.
It is said, on the day that Imam Hussain (as) died the skies and the earth 'wept blood'! SubhanAllah! And why wouldn't it! The Prophet had said "Hussain is from me and I am from Hussain", he and his family were incredibly special and loved by the Prophet and we should do the same!
[qs:3:169]
"How many people find fault in what they're reading and the fault is in their own understanding" Al Mutanabbi