This came after a reconnaissance mission by his vassal Hanuman, who had been able to locate his wife.  
His youngest brother Shatrugan is rarely mentioned.  In the process of gathering an army, he helps Sugreeva come to the thrown and is aided by Sugreeva's blacksmith, Nala.  With the assistance of Nala he is able to construct a bridge of logs and debris to cross the ocean.  This came after a reconnaissance mission by his vassal Hanuman, who had been able to locate his wife.  With this information he invades the capital of Ravana and rescues his wife, Sita.  FTP, name this avatar of Vishnu and namesake of a Hindu epic.
His youngest brother Shatrugan is rarely mentioned.  In the process of gathering an army, he helps Sugreeva come to the thrown and is aided by Sugreeva's blacksmith, Nala.  
Rama