Man vs. Orc or Good vs. Evil may be the central conflict of The Two Towers, but right by its side we have another battle, one of the powers of industrialization and the natural world. Maybe this theme should be Wizards and the Natural World, because it's Saruman who's causing all the ruckus with his massive forges, which churn day and night fueled by the fresh corpses of huorns as they create swords and spears and axes.
These cold, lifeless works of iron meant only to kill, are made in exchange for the thriving forest of Fangorn, where the ents much watch their brethren burn. This is a classic battle of modernization, where the demands of war have forced new technologies at the expense of the natural world. But as the angry Angren River pours in when released by the ents, we see that Saruman's scheming was but a scratch in the old, might land of Middle-earth.
Saruman's exploitation of the natural world is an allegory for the industrialization demanded by the First World War. Tolkien is using the "bad guys" as industrialists to argue against this kind of destruction for the purpose of war.
In contrast to the orcs, who consume the nature around them (like the barren plains of Mordor), the elves are shown living in great harmony with the natural world. Men are somewhere in between, building large cities and fortresses, but leaving their land still intact.
We might as well call this theme "hope," because that's what perseverance is all about in The Two Towers. Hope in the strength of men and elves, hope in the power of good to triumph over evil, hope in your friends and companions, hope in yourself—there are so many things to hope for. And so much hope is required as things aren't going too well in Middle-earth.
Let's face it. Hope isn't something people talk about when it's a happy, peaceful time. Hope is something you turn to when your present reality is looking grim. Maybe relying on this abstract idea that everything will be okay in the end is a harmful kind of optimism, but in LotR, hope is all they have left when orcs are knocking down their doors.
Hope is just a word used to manipulate the hearts and minds of people. Hope is never concrete, it is purposely vague and distant and exists only in the minds of those people foolish enough to give it meaning.
Hope is a necessary condition for victory. It is prophetic in that things hoped for will come true, not in a mystical sense, but because those who hope for it will see it through. Without hope, there is no cause for the efforts of man.
Surprise, surprise. The Two Towers is a war movie. War is what drives the whole plot. All of this Ring bearing nonsense may seem really important, but it wouldn't be necessary if Sauron wasn't planning or re-taking over the world. The Ring had lain dormant for 2,000 years, but war has now forced the hand, and arms, of the free people.
But just because men don't want to go to war doesn't mean they won't do so, and do so with gusto. Between the speared orc head and Théoden's rousing speech, there's no lack of thirst for blood on the side of the good. Besides, in war and in death, sides don't matter too much.
There is only selfishness in warfare. The elves are reluctant to send a small company to Helm's Deep while Théoden doesn't even consider calling for aid from Gondor. It is every nation for itself.
The loss of life from battle must be weighed against the possibility of the loss of an entire nation. Sending soldiers out to die at the hands of the enemy is senseless when the people of a nation aren't under immediate threat.
We're not talking about buying only Apple products even after watching the Steve Jobs biopic. We're talking some serious, wartime pacts and bonds where the difference between trust and deceit is life and death. Where would Saruman be without the loyalty of the orcs and the wildmen and his faithful servant Wormtongue? Sure, Saruman is evil and manipulative (just like the person he's loyal to), but loyalty doesn't have to stem from love and kindness.
Unless it does. Sam is probably the most loyal character in The Two Towers. He's never left Frodo's side since they started their adventure, and doesn't plan on it, especially with Gollum lurking around. But even Gollum seems to be loyal to Frodo, who has treated him so well. It's Frodo we're worried about, as his loyalty wavers between his mission to destroy the Ring and succumbing to the weight of his burden.
Loyalty is something earned. By having empathy for Gollum and showing him sincere kindness, Frodo has earned Gollum's trust and his service.
Loyalty is always self-serving. Gollum serves Frodo to get the rope from around his neck, not because he has any pity on the new Ring bearer. If anything, he is jealous of him and will turn on him the moment he has a chance.