The possibilities of a second Martian invasion, probably
taking place around the time of World War I. Assuming (over optimistically)
that the Martians are able to fortify themselves against Earth's germs, that
still leaves them with the element of surprise shot, and up against an enemy
that now has poison gases of their own (chlorine, phosgene, and mustard), gas
masks and protective clothing, Fighting-Machines of their own (tanks and
armored cars), several flavors of flying machine (airplanes and zeppelins),
long-range and quick-firing artillery pieces, recoilless guns, submarines, and
all-big gun (Dreadnought-type) battleships.
The biggest handicap the Martians will face is that it
takes many hours to break out of their cylinders, during which time humans can
blast them with explosives of some sort. They could also position a cannon or
machine gun right in front of the screw, to fire directly into the cylinder as
soon as the screw falls out and slaughter the occupants. About the only thing
the Martians could do is land in the most out-of-the-way places they can find,
hoping that the human defenders won't have time to reach and attack the
cylinders before they are opened. But under the new conditions, the humans have
bombing aircraft to quickly attack the invaders wherever they land, and until
the cylinders are opened, their occupants can't even shoot back. Landing on
small, distant islands also leaves them vulnerable to fire from naval
artillery.
It's believable that the second wave would be more heavily
equipped than the first, given that those planning the invasion would have
expected the first wave to establish a beachhead in England that would then be
reinforced with further supplies and personnel. Possibly more powerful fighting
machines, and construction tools to allow for setting up a long-term base on
Earth.
You could have an ongoing battle starting up between the
Martian Second wave, and the rest of the world's nations (United against this
new threat) all in a WWI-esque setting. Humans would have advanced enough to
put up more of a fight against the original book Martians, (Gas masks,
howitzers, machine guns, land mines, rifle grenades, biplanes, ect. ect.) and
we can see huge land/sea/air battles between the desperate humans and the
entrenched Martian foes.
They'd need to land in a rather remote and isolated area
to avoid being blown up before they're ready to move.
The Black Smoke poison gas the Martians use is a simple
asphyxiating agent, so ordinary gas masks are sufficient protection against it.
This takes away the Martians' biggest advantage, as the Black Smoke was more
decisive than the Heat-Ray in their campaign of conquest. Against hidden and
entrenched artillery, the Martians now have no choice but to advance into the
humans' line of fire and take their licks until they can bring their Heat-Rays
to bear.
We know absolutely nothing about the flying machine the
Martians have, including its speed, range, and whether or not it is armed. If
the Martians don't expect aerial opposition, they might content themselves with
a relatively slow device that Earth's biplane fighters could successfully
engage. (Remember, Mars is running low on resources, so they'd probably scrimp
on their war preparations whenever they think they can safely get away with
it.) Antiaircraft guns will also be a factor now, when the flying machine attacks
cities and ground forces.
Some say that the Martians learned their lesson about
engaging warships with the "Thunder Child" incident, and thus would
now automatically fire on all warships at long range. But maybe they DIDN'T
learn their lesson. The third Fighting-Machine had disappeared by the time the
smoke cleared, so we don't know whether it walked away or got caught in the
blast radius of the Thunder Child. Add to that the fact that the flying machine
only turned up AFTER the battle, and we can see that the Martians might not
have had any witnesses to tell them what happened.
It may not matter, anyway. The Thunder Child steamed in
close before firing to presumably make every shot count, but with
battleship-sized guns, she could also have fired on the Martians from miles
away. And here's another thing to remember: pre-dreadnought battleships had
only two to four battleship-sized guns, while carrying large numbers of smaller
guns of various calibers. Capital ships of the Dreadnought era carried anywhere
from eight to ten or even twelve guns of the largest type, relying almost
entirely upon them during combat. That means that they would be far better
suited to a long-range duel with the Fighting-Machines than the Thunder Child
and her contemporaries were.
Physics doesn't always favor the technologically-advanced,
either. Energy beams like the Heat-Ray have a major weakness against
projectile-firing weapons of older type: they can only fire straight ahead.
Indirect fire is impossible to them; a beam of light will only bend if it is
near a black hole, and if the Martians wind up near one of THOSE, human weapons
will be the least of their worries. Mortars, heavy artillery and howitzers,
naval gunfire, and even (against personnel caught outside of their machines)
bows, javelins, and slings can all be used to lob lethal fire at unseen
targets.
Finally, if the Martians hang around near coastal regions
or near large rivers, submarines could give them fits. The subs could sneak in
underwater, possibly at night, surface, and feed the Martians a few shells from
their deck guns before they even know they're around, then submerge and sneak
away when the alarm is sounded.