To start right off this is the map and its main objectives.

Allies first spawn at the Train Cars:
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They have to make their way through to the Forward Bunker and destroy either the east or/and west wall:
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When done so, their main objective is to capture the flag to get a new spawnpoint at the Forward Bunker Flag and another one Downstairs:
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Now they need to construct the Door Controls & by that they will secure the Forward Bunker and stop axis from recapturing it:
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Now the first Golddoor opens and allies can steal the first of two goldcrates that need to be secured:
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They should secure the goldcrates at these doors , which are opened by the just constructed door controls but need to be defended, as axis can close them again:
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When Allies have secured both goldcrates they have won the map.

There are always a minimum of two ways to get to the objective but those you have to find yourself :P