There is a gap of about 12 years after Ezra's arrival in Jerusalem; compare 2.1 with Ezra 7.8.
v1: Nehemiah was another exile, living in the citadel in Susa. He served the king, see 2.1.
v2: Hanani, a brother of Nehemiah, arrived from Jerusalem. The wording here suggests that Nehemiah took the initiative in asking about the state of Jerusalem. This reflects his concern for the glory of God, as God's glory was always connected with the state of Jerusalem.
v3: The hopefulness and progress under Zerubbabel and Ezra was replaced by "great trouble and disgrace". No doubt God had raised up Nehemiah for such a time as this.
The wall of Jerusalem speaks of unity, strength, and security, Ps 122. Together with the temple it was a visible testimony of the blessing and presence of God amongst His people (Ps 84).
v4: Nehemiah's response, like Ezra's, was to pray. He did this before taking action. This was personal spiritual preparation, "for some days", about 3 months, from Kislev (v1), to Nisan (2.1); such a contrast with brief, superficial, rushed devotions. Here was whole-hearted devotion to God; mourning fasting, weeping, as in Ezra 9.5.
Nehemiah prayed to the God of Heaven; he knew to whom he was speaking.
v5: Nehemiah's first words were simply a declaration of what God is like; this is worship.
v6-7: "Let your ear be attentive", not presuming upon God, but trusting that He is merciful. Nehemiah identified with the sins of the people, and he prayed "day and night", coming before God persistently and regularly.
v8-9: Nehemiah knew something of God's word, and he used it in his prayer; the Lord had been faithful to His promise by judging the people, and sending them into exile. He had now been faithful in bringing them back to Jerusalem. Nehemiah's request was that He would honour their repentance.
v10: God had shown His redemption and power through His people; Nehemiah's prayer was that He would do so again. God is faithful to His own people.
v11: Others were praying also; Nehemiah knew he was not alone; there was still a faithful remnant.
Nehemiah had the trusted position of being the king's cupbearer; this gave him the ear of the king. A number of the Jewish people had been loyal servants of the Babylonians, Medes and Persians; Daniel, Mordecai. Although the nation had been dispersed, these individuals had, through their blameless lives, earned respect in the sight of the enemies of the people.