The Combined Forces
يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ ٱذْكُرُوا۟ نِعْمَةَ ٱللَّهِ عَلَيْكُمْ إِذْ جَآءَتْكُمْ جُنُودٌ فَأَرْسَلْنَا عَلَيْهِمْ رِيحًا وَجُنُودًا لَّمْ تَرَوْهَا ۚ وَكَانَ ٱللَّهُ بِمَا تَعْمَلُونَ بَصِيرًا
O you who have believed, remember the favor of Allah upon you when armies came to [attack] you and We sent upon them a wind and armies [of angels] you did not see. And ever is Allah, of what you do, Seeing.
Nearby ayahs help place verse 33:9 in sequence and meaning.
وَإِذْ أَخَذْنَا مِنَ ٱلنَّبِيِّـۧنَ مِيثَـٰقَهُمْ وَمِنكَ وَمِن نُّوحٍ وَإِبْرَٰهِيمَ وَمُوسَىٰ وَعِيسَى ٱبْنِ مَرْيَمَ ۖ وَأَخَذْنَا مِنْهُم مِّيثَـٰقًا غَلِيظًا
And [mention, O Muhammad], when We took from the prophets their covenant and from you and from Noah and Abraham and Moses and Jesus, the son of Mary; and We took from them a solemn covenant.
لِّيَسْـَٔلَ ٱلصَّـٰدِقِينَ عَن صِدْقِهِمْ ۚ وَأَعَدَّ لِلْكَـٰفِرِينَ عَذَابًا أَلِيمًا
That He may question the truthful about their truth. And He has prepared for the disbelievers a painful punishment.
إِذْ جَآءُوكُم مِّن فَوْقِكُمْ وَمِنْ أَسْفَلَ مِنكُمْ وَإِذْ زَاغَتِ ٱلْأَبْصَـٰرُ وَبَلَغَتِ ٱلْقُلُوبُ ٱلْحَنَاجِرَ وَتَظُنُّونَ بِٱللَّهِ ٱلظُّنُونَا۠
[Remember] when they came at you from above you and from below you, and when eyes shifted [in fear], and hearts reached the throats and you assumed about Allah [various] assumptions.
هُنَالِكَ ٱبْتُلِىَ ٱلْمُؤْمِنُونَ وَزُلْزِلُوا۟ زِلْزَالًا شَدِيدًا
There the believers were tested and shaken with a severe shaking.