StarWars.com talks to design supervisor Kevin Jenkins about what went into the design of these new vehicles for
The Last Jedi
The AT-M6
The new gorilla-like walker features a massive MegaCaliber Six cannon on it's back (hence the name), as well as armored front legs, to prevent tow cable takedowns. AT-AT's are 1/2 to 1/3 the size of these , and act as scouts for them.
The First Order Dreadnought
,img src='https://jediinsider.net/g/generated/Movies/Episode_8/Vehicles/star-wars-the-last-jedi-first-order-dreadnought-wideshot-1024x731__scaled_600.jpg"
The Mandator IV-class warship is an armored gun platform, which features " ..two enormous orbital autocannons for large-scale bombardments and 24 point-defense anti-aircraft cannons on its dorsal surface'" It is "about two-and-a-half times the size of a standard Star Destroyer."