We were discussing the Anukramanika Parva of Mahabharata, the very first Parva.
A brief idea of what Mahabharata is all about.

Now we will proceed onto the Parva Sangraha Parva.
Kurukshetra has another name- समन्तपञ्चकम्

The Rishis wanted to hear about Samantha Panchakam, Kurukshetra.

So, they asked Sauti, Ugrashrava.

Ugrashrava started narrating.

Why did the Rishis want to hear about Samantha Panchaka?

Because at the beginning Sauti had mentioned that after he heard Mahabharata being narrated by Vaishampayana at the venue of the Sarpa yajna of Janamejaya, he roamed around several Punya kshetras.

Among them was Samantha Panchakam.

बहूनि सम्परिक्रम्य तीर्थान्यायतानि च
समन्तपञ्चकं नाम पुण्यं द्विजनिषेवितम्
गतवानस्मि तं देशं युद्धं यत्राभवत् पुरा

Vaishampayana, when he told that this is where the battle took place, where the battle between good and evil took place and good won over evil, then Sauti wanted to visit that Punya kshetra.

Now, the Rishis wanted to hear more about Kurukshetra.

At the end of Treta yuga, the beginning of Dwapara yuga, Parashurama annihilated the vamshas of Kshatriyas over and over again, many times.

He was avenging the murder of his father, Sage Jamadagni by Kshatriyas.

This series of the destruction of Kshatriyas created five pools or lakes of blood in Kurukshetra.
That is why it is called Samantha Panchakam.

Parashurama offered tarpana with this blood to his Pitrus.

It is not that he was trying to establish his supremacy over the Kshatriyas.
He wanted to avenge the killing of his father and thereby satisfy his ancestors.

This was also in a way punishment to Kshatriyas for Brahma hatya which they should never have committed.

It all started when Kartaveeryarjuna came to Jamadagni’s ashrama and forcefully took away Kamadhenu who was obliging Jamadagni by giving milk for the yajnas that he kept on performing.

Being propitiated by what Parashurama did, Pitrugana such as Richeeka came to Parashurama and said: we are satisfied now, ask for whatever you want.

Parashurama said: I did all these in a rage.
I want to be relieved from this papa, this sin that I have committed, and also these five pools that I have created should become Punya tirthas.
They should become famous.
Then I will understand that my sins have been pardoned.

The Pitrus blessed that-may this happen-and they also told Parashurama that those Kshatriyas who are left on the earth should be pardoned now.
A small number, he should not harm them.

The area around these five pools is Kurukshetra.
This was the practice then, places were given names in accordance with the legends associated with them.

This is where the battle between Pandavas and Kauravas took place towards the end of Dwapara yuga, before the beginning of Kaliyuga.

This place has another specialty.
The land here is without any dosha, it is plain land without ups and downs, it is not a rocky land, it doesn’t have trees with thorns.

The term Samantha has another meaning.
During the battle of Kurukshetra, eighteen Akshauhinis of sena had assembled there.
One Akshauhini means a group of-1,09,350 foot soldiers, 65,610 horses, 21,870 chariots, and 21,870 elephants.

Eighteen such Akshauhinis.

As a matter of comparison, the Indian armed forces today are about 1.4 million personnel, which is about 14 Akshauhinis

In the battle of Kurukshetra 18 Akshauhinis participated.

And

समेतानां अन्तो यस्मिन् स समन्तः

They all perished there themselves.

That is how the name Samanta came.

When Sauti mentioned about- he is called Sauti because he is the son of the first Suta, Lomaharshana.
Sutaha – Sautihi – Suta’s son Sauti.
Elsewhere he is also called Suta because Suta is the name of the caste or position of the narrators of Itihasas and Puranas.

Rishis wanted to know about the various units of the army prevalent then.

The basic army unit was called पत्तिः – comprising of five soldiers, three horses, one chariot and one elephant.
This is similar to the Squad or the smallest army unit

This comes in Sri Rudram also;
The lord is addressed as – पत्तीनां पतये नमः

When three Pattis come together, it is called Senamukha, similar to a Platoon.

Three Senamukhas put together becomes Gulma, something like a Company.

Three Gulmas would make one Gana, similar to a Battalion.

Three Ganas would become a Vahini, like a Brigade.

Three Vahinis would make Pritana, like a Division in the army.

Just for comparison, I am saying this, not the exact numbers.

These terms appear in the Vedas also,

Durga Sukta – पृतनाजितं सहमानं उग्रं अग्निम्

Group of three Pritanas- Chamu.

Three Chamus- Anakini.

Ten Anakinis- one Akshauhini.

So, Akshauhini you can say is something similar to the Army Corps of today.

They were all so well organized, you see, with a specific hierarchy and line of command.

Not like what you see on tv, about a hundred or two hundred skinny soldiers running towards each other and fighting with swords and clubs at the center of the screen.

Look at the size, nearly 1.8 million soldiers, on top of those elephants, horses of corresponding numbers, they all perished in the battle of Kurukshetra in a matter of eighteen days.

Can you visualize this?

Out of these seven Akshauhinis were of the Pandavas – यदाश्रौषं अक्षौहिणीः सप्त युधिष्ठिरस्य.
So naturally, the other eleven Akshuhinis were of the Kauravas.