How should the prayers (salat) be performed in battlefield? How about when one is bleeding? How about when one is on a mission and must complete the mission within a given time frame and don't get time to perform salat?
First of all, I suggest you to read the verses of Surah al-Nisa which are as shown in below (that are related to your question):
إِذَا ضَرَبْتُمْ فِي الْأَرْضِ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُوا مِنَ الصَّلَاةِ إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُوا ۚ إِنَّ الْكَافِرِينَ كَانُوا لَكُمْ عَدُوًّا مُّبِينًا ﴿١٠١﴾
وَإِذَا كُنتَ فِيهِمْ فَأَقَمْتَ لَهُمُ الصَّلَاةَ فَلْتَقُمْ طَائِفَةٌ مِّنْهُم مَّعَكَ وَلْيَأْخُذُوا أَسْلِحَتَهُمْ فَإِذَا سَجَدُوا فَلْيَكُونُوا مِن وَرَائِكُمْ وَلْتَأْتِ طَائِفَةٌ أُخْرَىٰ لَمْ يُصَلُّوا فَلْيُصَلُّوا مَعَكَ وَلْيَأْخُذُوا حِذْرَهُمْ وَأَسْلِحَتَهُمْ ۗ وَدَّ الَّذِينَ كَفَرُوا لَوْ تَغْفُلُونَ عَنْ أَسْلِحَتِكُمْ وَأَمْتِعَتِكُمْ فَيَمِيلُونَ عَلَيْكُم مَّيْلَةً وَاحِدَةً ۚ وَلَا جُنَاحَ عَلَيْكُمْ إِن كَانَ بِكُمْ أَذًى مِّن مَّطَرٍ أَوْ كُنتُم مَّرْضَىٰ أَن تَضَعُوا أَسْلِحَتَكُمْ ۖ وَخُذُوا حِذْرَكُمْ ۗ إِنَّ اللَّـهَ أَعَدَّ لِلْكَافِرِينَ عَذَابًا مُّهِينًا ﴿١٠٢﴾
فَإِذَا قَضَيْتُمُ الصَّلَاةَ فَاذْكُرُوا اللَّـهَ قِيَامًا وَقُعُودًا وَعَلَىٰ جُنُوبِكُمْ ۚ فَإِذَا اطْمَأْنَنتُمْ فَأَقِيمُوا الصَّلَاةَ ۚ إِنَّ الصَّلَاةَ كَانَتْ عَلَى الْمُؤْمِنِينَ كِتَابًا مَّوْقُوتًا ﴿١٠٣﴾
And when you travel throughout the land, there is no blame upon you for shortening the prayer, [especially] if you fear that those who disbelieve may disrupt [or attack] you. Indeed, the disbelievers are ever to you a clear enemy. (101)
And when you are among them and lead them in prayer, let a group of them stand [in prayer] with you and let them carry their arms. And when they have prostrated, let them be [in position] behind you and have the other group come forward which has not [yet] prayed and let them pray with you, taking precaution and carrying their arms. Those who disbelieve wish that you would neglect your weapons and your baggage so they could come down upon you in one [single] attack. But there is no blame upon you, if you are troubled by rain or are ill, for putting down your arms, but take precaution. Indeed, Allah has prepared for the disbelievers a humiliating punishment. (102)
And when you have completed the prayer, remember Allah standing, sitting, or [lying] on your sides. But when you become secure, re-establish [regular] prayer. Indeed, prayer has been decreed upon the believers a decree of specified times. (103)
Of course it has not illustrated in detail, but in according to the Sunnah of the prophet Mohammad (SAWW) (from the view of Shia) :
The prayers which are 4Rek’ahs, they will change to 2Rek’ahs. The first group do a Rek’ah with the Imam, and the Imam will be stop after the first Rek’ah, and that group will do the other Rek’ah lonely and will come back to the war, afterwards the second group will go to their place and do a Rek’ah of their prayer with the Imam and do the second Rek’ah lonely.
Tafseer-e-Nemune, Volume4, page103.
Of course there are other views regarding the circumstances of it, but it was the most famous of them.
- There's no specific prayed mentioned particularly during battle except the prayer of fear, or salatul khawf.
It's collected in both Bukhari and Muslim, that during the battle of Dhat Riqa:
"... a group formed a row and prayed along with him (the Prophet), and a group faced the enemy. He led the group which was along with him in a rak'ah, then remained standing while they finished the prayer by themselves. Then they departed and formed a row facing the enemy. Then the second group came and he led them in the remaining rak'ah, after which he remained seated while they finished the prayer themselves. He then led them in salutation."
The prayers are shortened during battle.
- There's no prayer prescribed while one is bleeding.
- The prayer can be shortened depending on the travel length.