side by side

adjective

two entities are next to each other and oriented so that their sides are adjacent to each other

arrangement of people or items to the side of one another, facing the same direction

Beside or alongside one another; close to one another and abreast.
“The new houses were built side by side, facing the lake.”
“The structure was examined and passed by the Board of Trade in February, 1890, after it had been tested with two trains of 50 loaded wagons, each hauled by two engines, and pushed by a third. The trains ran side by side, and their combined weight, including the six engines, was 1,800 tons. The deflections of the girders were precisely in accordance with the calculations of the engineers.”
In peace.
With a common purpose.
“The soldiers of XX and YY were fighting side by side against a common enemy.”