Invasion is a campaign. Like any campaign, Invasion has phases to its campaign that must be accomplished in linear sequence. The Invasion Play List Maps consistently present a realistic campaign scenairo along three phases of Game Play. Tier 1: the landing of the invasion forces to breach the outer barrier to the enemy strong hold; Tier 2: the breaching of the enemy strong hold to expose the data Core; and Tier 3: the theft of the data Core from the enemy strong hold to a neutral location for friendly extraction. It is a strong Story of a campaign that makes Invasion unique among its peers.
UPDATE: These lessons were based upon the original three Play List Maps: Breakpoint, Boneyard, and Spire. All references to Play List Maps within these lessons refer exclusively to those three maps and none of the community maps.[1]
Without presenting a Story, a map that loads customs with the Invasion Game Type is no more Invasion than Invasion Slayer is Invasion. Without a Story that is intuitive, there is no campaign, and thus no Invasion. But there are other Game Elements that the Game Type and Play List Maps combined together present that make Invasion unique as well.
For example, just as you would never forge an Assault Map without a bomb goal to arm the bomb with, you would never forge an Invasion Map with only one Territory Objective, because you need two Territory Objectives to divide the three Defender Teams between. Dual Objectives is a fundamental Game Element of Invasion and is a concept that primarily focuses on offensive strategy.
Through out these lessons, we will study the various Game Elements that the Game Type and Play List Maps present; not to identify what we want to forge into our Invasion maps or how to forge them into our maps, but more importantly why we forge those concepts - to identify the ends we expect to achieve from those means that we forge. It would be better to forge to a goal than to forge to a series of do's and don'ts. The latter approach quite often satisfies a check list, but misses the intent of Invasion by a country mile.
Summary
Invasion is a campaign and presents a campaign of three phases.
Invasion maps requires both a strong Story and proper Game Elements to play Invasion.
Our focus will be on why we forge specific concepts into our maps so we can see what it is we are trying to accomplish.
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[1] At least one of the community maps introduced into Match Making fails to conform to the original intent of Invasion. (As you study these lessons, the non conformity will become clear enough.) For this reason, I do not intend to rely upon any community map to demonstrate how to forge Invasion.