SB 10.77.9
viksya tat kadanam svanam
nirupya pura-raksanam
saubham ca salva-rajam ca
darukam praha kesavah
Translation:
[Sukadeva Gosvami continued:] After He arrived at Dvaraka and saw how His people were threatened with destruction, and also saw Salva and his Saubha airship, Lord Kesava arranged for the city’s defense and then addressed Daruka as follows.
Purport:
Lord Krsna placed Sri Balarama in a strategic position to guard the city, and He also appointed a special guard for Sri Rukmini and the other queens inside the palaces. According to Srila Visvanatha Cakravarti, by a secret route special soldiers conveyed the queens to safety inside Dvaraka.