Why is fighting on the defensive such an advantage for untrained troops?
commanders can use more men.
inexperienced troops will not have to execute maneuvers.
they can perform maneuvers on the battlefield faster.

Inexperienced troops won't have to execute maneuvers, because they don't understand basic formations, so if the only thing they have to worry about is shooting or fighting, it increases their efficiency.

Explanation:

American strategists seem to agree on little these days, except to say that America is in grave danger. Some maintain that Iran is the root of all evil and believe that a final showdown in the Middle East is now inevitable since the Obama-era nuclear accord has been abrogated. Still more are anxious that a major war with North Korea is just around the corner because after all the probability of the Singapore talks succeeding is rather low. Journalists have begun to fret about an old question—once quite theoretical—concerning whether the U.S. military could “handle” medium-sized wars against both Iran and North Korea simultaneously.