I like an RTS where you take time to build a well-defended base and a decent army. It's how I play RTS games even though it's not the 'right' way, but one problem is that it makes every game last for hours. I almost split the game in two - 1)build a base 2)battle the enemies

The first part tends to be quite repetitive as well and while some people probably like that, I wondered how I can promote the "big base" approach without a mandatory 1 hour base-building phase at the start of each game?

Remove building times and come with a finite amount of resources perhaps?

That way, your base building will hit the ground running.

Also, you can sequence things as in Ground Control where reinforcements are shipped in waves, thus, there is no incentive to fire a first volley of troops to catch your opponent unawares (shifting the focus towards the 'puzzle box' of trying to maneuver units around enemy's units).

One thing that might become stale however: if both bases are sturdy from the get-go, then the game will be one of attrition as the defender will always be advantaged and no player will have the incentive to fight. In this scenario, I would recommend using a different approach...

What if all units are AI controlled and behave like a mob? That way, you can always focus on your base, and not worry about each player avoiding to send their troops.

As the game progresses, mobs on both end would become more powerful/numerous, so that only the 'best base' would stand. It looks a lot like a mirror tower defense now doesn't it?

Either you have the necessarity to build a base or not, everything else should be the choice of the player.

Turtler, player who turtle in their base, build up a large army and steam-roll the enemy, is not an uncommon type of player. Yet it is not the standard player.

The most basic tasks of a base are to be a safe haven for your weaker units and to contain and defend your important production buildings. This should lead to the necessarity to gain resources, to build up a production economy and to build defenses:

1. Hard to reach/protect resources. Maybe you need to fight over resources, therefor you need to leave your safe base in order to get your hand on these valuable, limited resources.

2. Raids from your enemies. Weak and unguarded units/buildings will get damaged/destroyed. The enemy will gain an advantage if you need to put more resources than necessary in your economy.

3. You need to get a working, cost-effective economy running to build and maintain a large army.

You should be challenging all of these topics. If you don't challenge one of these, your game could be too easy to win by just turtling. To add some variance to your level design, you can try to change the weights of the three topics, something like this:

- race for resources: the most important resources are reachable easily by all factions, you need to get a hold on them quickly

- tower defense: the enemy is pressing on from the start, wave after wave enemy units attack your base and you need to get a economy up under permanent pressure.

- counterstrike: the enemy is in a well defended base, you can't overrun the base in a single attack, even with the best units. Whenever you start an attack, a hard counterstrike will hit your base. You need a good working economy to keep up permanent pressure on the enemy.

Remove building times and come with a finite amount of resources perhaps?
That way, your base building will hit the ground running.

I don't think I'd want it to be like that the whole game, but some introductory "fast build" phase might be an idea. The first 5min you can build without time limits and only after that does the game properly 'start'.

You could have something blocking movement, and force the player to focus on base building because there is nothing other to do. There could be bad weather at the start, and from time to time during the game. The bad weather makes it difficult or impossible to go far away from from your base. Maybe they can't see, or they get lost, or something.

It doesn't have to be bad weather. I can also think of:

• drought - the troops can't go too far away from the base or they die of thirst.
• tide - water is blocking the way.
• night - the troops can't see without the light from your base.

If you reduce build times, you're basically giving a larger and larger advantage to the player with the best reflexes.

You could make the base building a separate offline step, sort of like building a deck in a card game. Or like the Wargame series of RTS, which has you choosing which forces to bring in a sort of deck like format. Given limited resources, a player could try to make a balanced base, a econ heavy base, or maybe skew themselves towards building a Level 2 or 3 unit at the start, at the cost of economy and defense.

You might also try something similar to Gratuitous Tank Battles, which is an asynchronous game where one player sends in an attacking force, and the other builds defenses. You could do something similar where one player is designated the attacker, the other the defender. Maybe give a countdown before the attacker can move out of their deployment, but it gives them time to build their forces and organize them. The defender could then build their base and defenses during that same period. You could also toss a timer on when the attack ends, which could keep the game from getting long. One could tally up damage or units lost, or give the attacker some goal, "Kill X important buildings". If that proves to be fast enough, one could even swap the attacker and defender roles in the same game.

One idea might be to replace "base-building" with "base-arranging". What I have in mind is this: each player starts out with a pre-determined set of moveable, building-like modules. Each by itself does little (it might perhaps have some minor purpose, such as mining or churning out simple units), but the real strength of these modules is that they can be arranged together to form compound structures with new properties and abilities--two arranged side-to-side might make an aerial-unit factory; two arranged diagonally might make a tank factory; three in an L-shape might make a defensive turret; and so on. The challenge, then, is not building up a base, but arranging the functionality of your base to best effect, and potentially re-arranging your base as the fight goes on.

The major problem with this, as I see it, would be the question of replacing destroyed modules. Perhaps the player could repair destroyed modules at some cost of resources and time, but would not be able to create new ones.

Some ideas:

Have an early defender’s advantage that diminishes as the game progresses. You could for example make powerful base defenses that are cost effective against early units, but are weak against upgraded or higher tier units like artillery and aircraft. Tech progression is often on a different timeframe compared to regular production, that way players can’t just spend more money to unlock tech faster. While each player is waiting for the offensively useful techs, they’ll want to spend their remaining money on base building and defensive units.

Tie the economy to base building. Normally, you have to expand to more vulnerable locations to increase your income, but you could make it so resources are mainly found near your original base and/or make it so that your initial base can be significantly upgraded (adding on new modules to your refineries or something, maybe even get income from the total “population” of your base) to increase your income. This would encourage building a single large base and make it harder to harass the other player’s economy early on, but you’d still have to have some change in pace later on (like superweapons or the higher tier offensive units above) to make sure both players eventually have an incentive to attack.

Similarly to what Thaumaturge said, I'd suggest non-traditional base-building. For example there are set points where bases can be built and there's a strong drive to discover those locations and build there as soon as possible rather than turtling. After that, you can destroy/take over other's bases. Perhaps the bases are powered by natural resources, e.g. a geothermal vent.

You could make the base building a separate offline step, sort of like building a deck in a card game.

This. Explicitly separate the phases. Every player starts out with a set amount of resources and before the game proper starts, is allowed to put together a base, but not move units or attack - they may only place units, which take an instant amount of time to build. When the players are finished, they proceed to the next phase, which is the actual battle. Basically you'd skip through the early game while removing the need for reflexes and set build orders through that phase.