How threadbare were the Colonial Marines on LV-426?

First, they don’t even take a full platoon. Just 2 squads.

Then they leave the Sulaco on auto-pilot and had to jury-rig a colony transmitter to remote pilot the back-up drop ship.

Lastly, no one realizes that the Marines are being sent into the colony hive, right below the primary heat exchangers. Only after both squads are down there does Gorman realize this and tells Apone to confiscate magazines.