It is a truism of celestial warfare that among the most valuable targets to seize in the course of a major planetary assault operation is the primary planetary starport or local starports close to the  intended target(s) of the operation. Starports, for all the obvious reasons, make perfect orbitheads, offering existing facilities eminently suitable for the landing and disembarkation of troops and materiel in quantity. (Orbital elevators, by contrast, are usually considered too fragile and susceptible to sabotage for this purpose, if the enemy are willing to absorb the ensuing damage to their own planet, until the orbitals and the continental area surrounding the elevator have been entirely secured.)

Why, then, are combat drops rarely, if ever, targeted at the vicinity of starports?

Again, it is important to remember that which is unseen. The popular image of starports is heavily biased towards the facilities for ground-landing starships – understandably, since the giant launch/landing pads built to handle nucleonic-thermal ships, with their blast-deflecting berms, “hot” shafts, and motile structures are some of the most impressive structures ever built – and towards the shuttleport terminals used by commuters and starship passengers alike. Nonetheless, the majority of cargo in the developed Worlds is carried by dedicated spacecraft incapable of atmospheric landing, to and from which cargo is transp0rted in high volumes using suitably cheap methods: either laser-launch/deceleration facilities, mass drivers, or both, in which case the former handles light or delicate cargo and the latter hardbulk.

What this means in military terms is that, any other defense grid aside, the majority of starports in the developed Worlds have at their disposal a multi-gigawatt-range phased-array laser system, and/or a pair of mass drivers capable of accelerating a solid slug the size of a shipping container (or, equally effective, a shipping container packed with rubble or cheap heavy-metal ingots) to orbital velocities – both, admittedly, equipped with safety systems designed to prevent them from being used in exactly the manner which is desirable for military purposes, but that is something usually corrected readily enough by a software change – along with all the high-resolution traffic-control sensor equipment needed to target them effectively.

It is also a truism of warfare in general that one shouldn’t stab a heavily-armed man in the front. That is doubly relevant when the things they’re using as weapons are also the value that you want to capture.

– Elementary Principles of Orbit-to-Ground Maneuver Plans, pub. INI Press