http://www.3plusplus.net/2012/11/6th-edition-changes-objectives-and-mobility/

Two very minor yet significant changes in 6th edition is the interaction objectives have with the rest of the game system. This is one thing I am a bit worried about with the 3++con missions as I have removed this restriction in some parts and believe I may have to rescind this decision (but don't really want to!).

What I'm talking about here is objectives can now be placed within 6" of the board edge and table halves are decided for players BEFORE objectives are placed. What this often ends up doing is putting multiple objectives around the edges of midfield rather than more towards midfield as opponent's try to keep objectives in more difficult to reach places for each other.

With the five and six objective missions, this is less of an issue as there is finite space along board edges and some objectives end up getting pushed more towards the middle but particularly with the Hammer & Anvil deployment, objectives can often be far apart and closer to army starting positions more often than not. This does a couple of things. First, it means you need to understand objective placement even more. (This is something we've aimed to bring back with 3++con rather than having set objectives all the time – we've often combined the two practices in fact.) With more space to place your objectives and greater scope of being able to place objectives within your deployment zone (WHICH YOU KNOW), being able to place objectives smartly is really important.

Secondly, it changes how game mechanics interact. A lot of really dumb people are trying to claim 6th edition is a static game and then go on to refer to how 5th edition was static, too. They then often point out the "crapness" of vehicles as the main reason 6th edition is static and gunlines therefore rule. Beyond the fallacy inherent in that argument... such a stance means you have one real tactic: shoot the enemy off objectives. Given that shooting is such a strong option this doesn't seem like such a bad idea but what it's forgetting is that movement is what sets shooting up.

It's very easy to keep squads alive now as you can only kill models you can see (except with blasts). Between vehicle wrecks and terrain it should be impossible NOT to be able to hide a single model from a certain degree of angles. If you don't have mobility or the ability to move and fire, you don't have the capacity to actually overcome this very basic concept and your static gunline army gets LOL'd at by a single Gretchin.

What does this have to do with objectives being 6" closer to the board edge? It reduces the angles with which you can flank an opponent. If an opponent has a perfect 180 degree LoS blocking terrain piece which you have to flank to be able to see around, you have to go a further 6". That's an extra turn for infantry units and that can be the difference between the game continuing or the game ending. This isn't to say you MUST have vehicles but rather you MUST have mobility built into your army where your army can push towards your opponent, across midfield which may not have any game end significance (i.e. no objectives but is still important in board control) and into their deployment zone where their objectives might be sitting. All the while you'll have to be engaging your opponent during this time unless they are just letting you waltz across the board.

If you don't do this, or cannot due to your opponent stopping you, the game basically comes down to who gains the most secondaries or if playing in a mission with a larger number of objectives, who controls the objectives pushed out from deployment zones (where midfield might come more into play in terms of end game significance). This means two things:

1.You need to theoretically be able to get to your opponent's side of the board and stay there before Turn 5.
2.Secondaries are huge.
To further complicate things, only infantry units (without certain restrictions) can contest opposing objectives so the units which need to get across the board and survive, need to be on foot.

The implications of this are pretty far-ranging. Mobility is part and parcel of the game as it's the one thing you have the biggest control over. It also is the determining factor of where opponent models are removed from. It ensures your opponent has a harder time of hiding and allows you to potentially contest objectives which are further from the centre of the board. If you want to play a static gunline and just throw dice at your opponent, be my guest but don't be surprised when opposing players out play you and force you into bad situations due to your lack of mobility. Lots of guns are great but they need to be anchored by the concept of mobility.