atha vyavasthitaandhristhva dhaartaraashtraan kapidhvajaha |
pravrutte shastrasampatte dhanurudyamya paandavaha |
hrishikesham tada vaakyamidamaaha mahipate || 20 ||


Now, as he was about to take up arms against the battle-ready sons of Dhritrashtra, Arjuna – whose chariot displayed the emblem of an ape – spoke these words to Hrishikesha, O King.

atha :  thereafter
vyavasthitaan-dhristhva : observed that they were getting ready for war
dhaartaraashtraan : sons of Dhritraashtra
kapi-dhvajaha : flag with the emblem of an ape
pravrutte : while about to engage
shastra-sampatte : releasing of weapons
dhanur-udyamya : taking up his bow
paandavaha : Arjuna
hrishikesham : Hrishikesha
tada : then
vaakyam-idama-aha  : spoke these words
mahi-pate : O king
Did you observe something different here? By now if you have attempted to read aloud any of the shlokas, you realize that they usually follow the same pattern – 2 lines per shloka, 2 quarters per line, 8 syllables per quarter. But in this shloka, we see for the first time that there are 3 lines instead of 2.
This pattern or “meter” is changed every so often to indicate that the listener should play close attention to a particular shloka, or the shlokas that follow.
Let’s also look at another aspect that this shloka highlights. The core of the Gita is a dialogue between Shri Krishna and Arjuna. In ancient Indian literature, there exists a tradition of beginning important teachings or messages with the word “atha” which means now. The shlokas so far covered introduction and background, but now, Arjuna starts the dialogue in the next verse, hence the word “atha” is used here.
1. The meter followed in the Gita is called “Anushtup Chhanda”
2. Each chapter of the Gita concludes with a sentence that acts as a marker signifying the end of the chapter. These traditions were followed as a means to make memorization easier, among other things. Every end-of-chapter market contains the phrase “Shri-Krishna-Arjuna-Samvade” which means “a dialogue between Shri Krishna and Arjuna”