The Victory
وَأُخْرَىٰ لَمْ تَقْدِرُوا۟ عَلَيْهَا قَدْ أَحَاطَ ٱللَّهُ بِهَا ۚ وَكَانَ ٱللَّهُ عَلَىٰ كُلِّ شَىْءٍ قَدِيرًا
And [He promises] other [victories] that you were [so far] unable to [realize] which Allah has already encompassed. And ever is Allah, over all things, competent.
Nearby ayahs help place verse 48:21 in sequence and meaning.
وَمَغَانِمَ كَثِيرَةً يَأْخُذُونَهَا ۗ وَكَانَ ٱللَّهُ عَزِيزًا حَكِيمًا
And much war booty which they will take. And ever is Allah Exalted in Might and Wise.
وَعَدَكُمُ ٱللَّهُ مَغَانِمَ كَثِيرَةً تَأْخُذُونَهَا فَعَجَّلَ لَكُمْ هَـٰذِهِۦ وَكَفَّ أَيْدِىَ ٱلنَّاسِ عَنكُمْ وَلِتَكُونَ ءَايَةً لِّلْمُؤْمِنِينَ وَيَهْدِيَكُمْ صِرَٰطًا مُّسْتَقِيمًا
Allah has promised you much booty that you will take [in the future] and has hastened for you this [victory] and withheld the hands of people from you - that it may be a sign for the believers and [that] He may guide you to a straight path.
وَلَوْ قَـٰتَلَكُمُ ٱلَّذِينَ كَفَرُوا۟ لَوَلَّوُا۟ ٱلْأَدْبَـٰرَ ثُمَّ لَا يَجِدُونَ وَلِيًّا وَلَا نَصِيرًا
And if those [Makkans] who disbelieve had fought you, they would have turned their backs [in flight]. Then they would not find a protector or a helper.
سُنَّةَ ٱللَّهِ ٱلَّتِى قَدْ خَلَتْ مِن قَبْلُ ۖ وَلَن تَجِدَ لِسُنَّةِ ٱللَّهِ تَبْدِيلًا
[This is] the established way of Allah which has occurred before. And never will you find in the way of Allah any change.