The Allies troops must capture the bridge intact to establish a bridgehead. The Axis has twice failed demolition of the bridge and must now try to recapture it, to avoid the Allies from entering the German Vaterland.
To capture the bridge, you will need to capture the 5 objective. Towers, Pier, Center, Pier and Towers.
As you capture more objective, you will move your reinforcement forward, closer to the battle. And eventually push the the enemy reinforcement backward.
Watch out for sniper fire on the bridge, it appears to come from the top of the superstructure, so seek cover in the open train cars. The service tunnel is close quarter combat so SMG is effective.
On 7th of March 1945, the last months of World War II, elements of the US 1st Army approach the last standing bridge over the Rhine River, the Ludendorff Bridge at Remagen.