With SEOW v3.2, spy units have been introduced to the order of battle for the first time. Any vehicle object can be class as a spy unit (object class "VSP"), but by default the Bicycle object is used as the sole spy type. In a nutshell, spies are used to gather recon information. Here are the details.
Spies have mobility
All spies will move with Simple Complex Ground Movement Mode. This means that they will ignore roads, bridges, rivers and forests and will move in a straight line between waypoints. Although they move slowly, they can go anywhere.
Spies have excellent eyesight
All spies have extended reconnaissance detection ranges. They gather information on all enemy units and industrial facilities up to many kilometres distance. The actual scale is determined by the Spy_Scale field in the Sector_Recon_Parameters table. By default this number is 3 or 4, meaning 3 or 4 times the Control Radius or more. You can place a spy in a forest about 10 km away from an industrial centre and it will return growing amounts of recon information over the following missions, depending on the recon decay setting for industrial infrastructure.
Spies are hard to find
Spies are invisible to air recon photos, so you just cannot send aircraft out taking heaps of photos to find enemy spies - that will not work. On the ground, enemy combat units need to get very close to a spy (less than 200 m) to detect it in the recon sense. Enemy political units (staff cars etc) are better at finding spies, but still they need to get within 500 m or so. The political unit types are hard-coded in SEOW v3.2. They are the following objects: Bicycle, OpelKadett, GAZ_M1, VW82, VW82t,WillisMB, WillisMBt, WillisMBtc_US, WillisMBt_US, WillisMB_US, Kurogane, Limosine, BlueCar, BeigeCar. Basically the idea is to set a spy to catch a spy.
Spies are self-sufficient
Spies will expertly steal supplies from enemy fuel dumps and supply drops. Once located properly close to supply resources and near airbases or other places of activity, they will provide a steady stream of recon information unless detected and killed by the enemy.
Spies are paratroopers
Spies are able to be deployed as paratroop units. That is they can be dropped from air transports behind enemy lines, or can be flown in on glider missions. They can also simply ride into enemy territory using their excellent mobility in rugged terrain to avoid discovery.
Spies can be produced industrially
Spies, like all other units, can be made through industrial effort and commissioned as reinforcements in the usual way.
Spies are easy to kill
Spies, as bicycle units, are quite defenceless and are easy to kill once discovered. They can even be "caught and killed" by enemy units if the enemy units happen move within engagement range and open fire. For this reason, never place your spy near a road that enemy troops may use. Keep them out of harm's way. Spies are never captured alive and are thus never interrogated.
How to give other units spy capability
The spy's scouting function is dependent upon the object class "VSP". You can make any vehicle a VSP class unit by editing the Object_Specifications table. Also not that the extended recon range for VSP class units is governed by the Spy_Scale field of the Sector_Recon_Parameters table. The larger that value, the longer the range that spies can gather recon over.
Here is a graphical example of spy placement to support an armoured assault. The Japanese forces have placed a spy west of Kamen Rybolov in the Lake Hanka region of the Manchuria sector. Over time the spy has collected 52% recon on the local Soviet controlled airbases, showing that there is no serious ground defence (only some barrage balloons). The base should be easy to capture if the approaching Japanese tanks to the south can move swiftly and destroy the balloon units before the enemy IL-2s can intervene. Twenty enemy aircraft could be captured!