This method of second language instruction was a further development or evolution of The Direct Method. World War II rose up and slapped the U.S. government in its linguistically challenged face, waking it to the need and definite lack of language competency to deal with the other nations of the world. Apparently, the U.S. continues to find itself in this position with International conflicts. The lesson has to be relearned over and over again that bilingual fluency is crucial for Americans. Without it, other nations, some of which are our enemies, have the distinct advantage.
The Audiolingual Method incorporated much from The Direct Method. To that method, it added the concept of recognizing patterns within languages to try and teach communication ability within the target language. Drills and extensive repetition exercises were used to impart an "over learning" of the material that could impart the patterns of the language and, hopefully, make automatic responses within the minds of the student when hearing and speaking the language.
To facilitate this, one engages in a lot of memorization of dialogues in the target language, complex but useful drills, and grammar games. One technique used in this method, one that the Pimsleur Language products use, is the expansion or "backward build-up" drill.
This is where a sentence or new vocabulary word is broken down in parts or syllables. The student either starts from the end of the final word in a sentence and repeats each word within the sentence working backward or begins with the final syllable of the word and repeats each syllable, again working backward until the entire word is pronounced. This is highly effective when done correctly. You will see this used extensively in the Pimsleur and Learning Spanish Like Crazy courses.
The Audiolingual Method works and brings rapid success but is not without its critics. It was argued that this method was just rote memory work and did not take into consideration the emotional factors in second-language acquisition. This paved the way for newer methods.