What was the significance of blowing (sounding of) the transcendental conch-shells in the Kurukshetra war?

Question

Tasya sanjanayan harsham kuruvriddhah pitaamahah;
Simhanaadam vinadyocchaih shankham dadhmau prataapavaan. 12.

His glorious grandsire (Bhishma), the eldest of the Kauravas, in order to cheer Duryodhana, now roared like a lion and blew his conch.

Tatah shankhaashcha bheryashcha panavaanakagomukhaah;
Sahasaivaabhyahanyanta sa shabdastumulo’bhavat. 13.

Then (following Bhishma), conches and kettle-drums, tabors, drums and cow-horns blared forth quite suddenly (from the side of the Kauravas); and the sound was tremendous.

Tatah shvetair hayair yukte mahati syandane sthitau;
Maadhavah paandavashchaiva divyau shankhau pradadhmatuh. 14.

Then also, Madhava (Krishna), and the son of Pandu (Arjuna), seated in their magnificent chariot yoked with white horses, blew their divine conches.

Paanchajanyam hrisheekesho devadattam dhananjayah;
Paundram dadhmau mahaashankham bheemakarmaa vrikodarah. 15.

Hrishikesa blew the “Panchajanya” and Arjuna blew the “Devadatta”, and Bhima, the doer of terrible deeds, blew the great conch, “Paundra”.

Anantavijayam raajaa kunteeputro yudhishthirah;
Nakulah sahadevashcha sughoshamanipushpakau. 16.

Yudhisthira, the son of Kunti, blew the “Anantavijaya”; and Sahadeva and Nakula blew the “Manipushpaka” and “Sughosha” conches.

Kaashyashcha parameshwaasah shikhandee cha mahaarathah;
Dhrishtadyumno viraatashcha saatyakishchaaparaajitah. 17.

The king of Kasi, an excellent archer, Sikhandi, the mighty car-warrior, Dhristadyumna and Virata and Satyaki, the unconquered,

Drupado draupadeyaashcha sarvashah prithiveepate;
Saubhadrashcha mahaabaahuh shankhaan dadhmuh prithak prithak.18.

Drupada and the sons of Draupadi, O Lord of the Earth, and the son of Subhadra, the mighty-armed, all blew their respective conches!

In the Bhagwat gita chapter -1, verses 12 to 18, most of all (above mentioned fighters name) blew (to sound) their transcendental conch-shells (shankas) start of the Kurukshetra war.

• What was the significance of blowing (sounding of) the transcendental conch-shells by respective warriors?

Answer 1

Pāñcajanya (or Panchjanya) is the name of the conch (Shankha) in Hindu mythology which was blown by Krishna at the start of the Mahabharata War between the Kauravas and Pandavas at Kurukshetra, which was a Dharam-yudha (sacred war for the righteous) between the usurper King Dhritrashtra's hundred sons, the eldest being Duryodhana, and the five Pandavas (the cousins) supported by Lord Krishna himself.

Panchjanya when blown by Lord Krishna symbolised the war was won by the righteous Pandavas. Panchjanya is the udghosh, the sound of righteousness to be heard by the people of the world. Panchjanya is mentioned in the text 15 of the first chapter of Bhagavad Gita. Panchjanya, the great conch was a token of gift taken from Panchjana, the navigator in whose ship Srikrishna voyaged to rescue Sandipani's son.

It is said that when Krishna blows on His transcendental conchshell, the wives of the demons become subject to abortions, and the wives of the demigods become blessed with all auspiciousness. In this way, the sound of Krishna's conchshell used to vibrate and circulate all over the world.

Answer 2

From what I have read, there are two reasons:

1- The battle will start and possibly have enough luck to be victorious:

'Sanjaya said, "O great king! After some time, a tumultuous sound could be heard, when the warriors prepared to fight, and it made the heart tremble. There were the sounds of conch shells and drums.

2- To give a signal of a plan:

Sanjaya said, "I will tell you everything happened in that great battle. Listen patiently. All this is because of your own evil conduct. O Lord! Mentally, Krishna had already known earlier that the brave Satyaki would be defeated by the one with the sacrificial altar on his standard. 9 O king! Janardana knows the past and the future. O king! Therefore, the immensely strong one had summoned his charioteer, Daruka, and had given him instructions. 'Let my chariot be yoked for tomorrow.' 10 The gods, the gandharvas, the yakshas, ​​the serpents, the rakshasas and men can never defeat the two Krishnas. The gods and the siddhas, with the grandfather 11 at the forefront, know about the infinite prowess of those two. Listen to the battle, as happened. On seeing that Satyaki was without a chariot and Karna was attacking him with raised weapons, Madhava blew a rishabha note on his conch shell with great force. 12 From the sound of that conch shell, Daruka got the message. He took that chariot, with Suparna 13 decorating the standard.

Here Krishna tells Daruka that when Satyaki is without a chariot, Karna is attacking him and that the first one touches a note in his shell with great force, he will have to provide him with the personal chariot of Krishna. This shows that conches were also used to signal a plan.