Sena Niryana Parva is the fifty sixth Upa parva included in the fifth Maha parva named as Udyoga parva. Vaishampayana continued narration to Janamejaya in reply to his queries as follows.
What Krishna told to Yudhishtira after returning from Hastinavati?
Krishna returned from Hastinavati, reached Upaplava and resided in the camp of Satyaki. After his evening prayers and having food, he met with Yudhishtira. Krishna started discussions with him and called his Pandava brothers. Krishna told Yudhishtira about his attempts for avoiding war and to maintain peace in the society. He explained how he had come out of the court session hall when Duryodhana was about to order his arrest by Dushasana and Shakuni. He also explained about the helplessness of Karna and Vidura.
Then he announced the message of Kunti for Yudhishtira and her Pandava sons. Kunti had taught them with good education for conducting efficient public administration and social services but not for begging. He also conveyed the entire message to Draupadi. Since the military defensive arts were imparted to them by Drona, they were his disciples. The student should be more shining in the field of learnt subjects and the teacher when defeated by his own students in the same pedagogical field, he would certainly feel happier. The time for using the skills of Pandava brothers would be fast approaching, so conveyed to be cautious and prepared.
Who were the seven commanders in chief of the seven Akshohini soldiers?
The seven commanders in chief of the seven Akshohini soldiers were identified in consultations mutually. Yudhishtira was a capable warrior but not allotted any army leadership. Karna and Krishna were not participating as active soldiers in the war, hence Arjuna was also not allotted any army leadership. After honouring Krishna, Yudhishtira ordered the word ‘yoga’ as the soldiers would be aligned to march in the troops. Arjuna was in the front, leading the troops towards Kurukshetra. Yudhishtira was in the middle, sitting on the chariot fixed with a white umbrella to be seen by the entire troops, marching towards the Kurukshetra.
द्रुपदश्च विराटश्च दृष्टद्युम्नशिखण्डिनौ ।
सात्यकिश्चेकितानश्च भीमसेनश्च वीर्यवान् ॥
Meaning: Drupada, Virata, Drishtadyumna, Shikhandi, Satyaki, Chekitana and Bhima were the seven Commanders in chief for the soldiers for Yudhishtira.

The troops started, and were marching from Upaplava to Kuruksheta for a few days camping in the middle where water was available for them sufficiently.