Assalamu alaikum wa rahmatullahi wa barakatuhu!
In the Name of Allah, Most Gracious, Most Merciful
All of the Prophet Muhammad's (saw) noble characteristics were direct results of certain causes - such as his strong faith in Allah, his fear in Allah, and the complete trust he placed in Allah. In this regard, the characteristic of bravery is no exception.
The Prophet (saw) was a paragon of bravery because he feared no one save Allah, because he had faith in Allah's promise to protect him from his enemies, and because he placed his complete trust in Allah.
As such, he was like a great mountain, in that he did not easily shake or tremble, but instead remained firm and steadfast through the most harrowing of situations. His enemies threats did not perturb him; life threatening situations did not frighten him; and the threat of physical harm or even death did not faze him in the least.
He placed his complete trust in Allah, seeking no one's help save His help, being confident in His promise, and being satisfied and happy with His decree. With such wonderful qualities, it is not surprising that he personally fought in battles, placing himself in harm's way, even when few, if any, others were willing to do the same.
Never once did the Prophet (saw) flee from a battle; never once did he retreat even a single step when the fighting intensified. In fact, when heads were decapitated; when swords sliced through air, skin, flesh and bones; when many people met their deaths in a matter of minutes or seconds; when swords clashed with shields, and when arrows penetrated armour - the Prophet (saw) was the closest member of his army to the enemy. At times, the Sahabah (ra) used the Prophet (saw) as a shield, knowing that they would stand a better chance against their enemy if they rallied around the Prophet (saw).
For the Prophet (saw), it did not matter how many enemy soldiers there were on a battlefield; it did not matter how many weapons they had; these things did not matter because he believed with certainty that, regardless of the strength of the enemy, Allah would help him overcome them.
On the Day of Hunayn, most Muslims fled from the battlefield during the initial stages of battle. The only Muslims who remained steadfast on the battlefield were the Prophet (saw) and six of hid Sahaabah (ra); and this verse was revealed to him:
Then fight (O Muhammad) in the Cause of Allah, you are not tasked (i.e. held responsible) except for yourself, and incite the believers (to fight along with you) ..
(Surah Nisaa - Verse 84)
The Prophet (saw) was neither nervous nor frightened during times of battle; instead, he was calm and at peace, for he desired martyrdom at least as much as he desired victory.
As a result of the Prophet's (saw) bravery, he sometimes sustained injuries and lost many of his Companions (ra). And yet, he never became weak, cowardly or fearful; instead, he ploughed forward on the battlefield as if he wanted to die.
On the Day of Badr, he not only led his army, but also took part in the fighting during the most intense and dangerous stages of the battle. During the Battle of Khandaq, the Confederate armies were apparantly in complete control of the situation, confident that it was only a matter of time before they broke the siege and destroyed the Muslims of Madinah.
As for the Muslim soldiers, their hearts reached their throats, so afraid were they; they were shaken and put to trial, with at least some of them being on the verge of hopelessness. Meanwhile, the Prophet (saw) remained patient, steadfast and confident of victory.
But as confident as he was, he did not forget to invoke Allah for help. He stood up, prayed, supplicated, and invoked his Lord for help, until Allah answered his prayers and caused his enemies to be defeated, to suffer humiliation and to retreat in disgrace even though they greatly outnumbered the Muslims.
The violent wind that Allah sent to the Confederate armies instilled terror into the hearts of the polytheist soldiers, and thus the siege came to an end. And on the night of Badr, the Muslims fell asleep; as for the Prophet (saw), he stood up, prayed and invoked Allah for help.
No one was as brave as was the Prophet (saw), who said:
"By the One Who has my soul in His Hand, I would love to be killed in the way of Allah, to then be resurrected, and to then be killed again".
Wasalaam!