OCS play example

The hard core OCS fan will like this and likely have read it before. This is kindly reposted from BGG.

If you don’t understand how to use the reaction phase after this then OCS ain’t for you !;).

The following is a fairly detailed example of a Reaction Phase that includes Overruns, a Fighter Sweep, a couple of Hip Shoots, and some combat and fuel supply concerns. While plausible, the following situation is entirely contrived in order to allow me to cover areas of interest. Whether the following represents the best course of action during play is debatable, but every effort has been made to ensure that what is presented here is in accordance to the latest version of the OCS System rules (v4.0). Game specific rules, except where noted, are ignored.

The Russians have just finished the Supply Phase of their Player Turn and are in control of the village of Krasnoarmeysk which sits along the rail line that the Germans are using to supply their advance. The Germans would like to clear the village to open up the rail line as soon as possible and decide to press the issue during the Reaction Phase.

The Russian Pe.2 is stacked underneath the airbase marker to signify that it is Inactive.

The German plan of attack is to isolate Krasnoarmeysk in order to both cut off combat supply and limit any retreat options of the 24th Guards Division. Once that is accomplished air power will be called in to hinder the defenders before an Overrun is attempted to capture the village.First the Germans need to decide how they’re going to isolate the village. Since this is the Reaction Phase only ground units that are in Reserve Mode and Active aircraft are available to participate during the phase. They decide to release the 13th Recon Battalion who will then attempt to Overrun the 15th Infantry Regiment and block all supply from reaching Krasnoarmeysk.

The 13th Recon Battalion has a tracked Movement Point class (signified by its red Movement Allowance) and it needs to be fueled in order to move. The Germans have a couple of options of how to get that taken care of. The first option is to fuel the unit individually until the end of the phase at a cost of 1T, but since the 13th is part of a Multi-Unit Formation (signified by the bars running across the middle of the counter) another option is to fuel the entire formation by spending 1SP. Not only can this option be cheaper depending on the number of units that make up the Multi-Unit Formation, the fuel lasts until the next friendly Clean Up Phase, meaning that the units fueled using this option will not have to spend supply on fuel during their next player turn!

The Germans decide that it’s best to fuel the entire division, so 1SP is drawn from the dump and then thrown by the 4th Corps HQ to all of the Truck and Track Movement Point class units of the 13th Panzer Division. Although the Move Mode HQ can only throw supply forward five Movement Points, adjacent is good enough when it comes to supply, and all of the units of the 13th Panzer Division are fueled until the end of their next friendly Clean Up Phase.

The 13 Panzer’s Formation counter has been flipped to its fueled side and placed on the board as a reminder.

Now that the 13th Battalion is ready to roll, it heads out on a path towards the 15th Infantry Regiment and will attempt to Overrun it. Note that since the 13th was released from Reserve Mode during the Reaction Phase, it is only allowed to use half of its Movement Allowance. Once adjacent to its target the German player verifies that the unit still has the 3 Movement Points needed in order to conduct an Overrun and then declares the attack. At a quick glance the thought of having a unit attack another unit of equal strength may seem like a bit of a crazy move, but as we’ll see, combat isn’t always decided on raw combat strength alone.

The 13th has spent 1 MP to move into position for the Overrun.

Overruns follow the same exact procedure as regular Ground Combat as outlined to the right. We’ll follow this procedure step by step as the Germans resolve their Overrun.

STEP 1: Identifying the defending and attacking hexes is pretty straight forward, the Germans occupy 36.30 which is the attacking hex and the Russians occupy 37.31 which is the defending hex.

STEP 2: The Germans now need to pay 1T for combat supply in order to Overrun, but during their movement to get into position have moved out of their HQ’s throw range. In order for the attack to occur, they must use Internal Stocks and be marked with a Low Stocks marker (which is place underneath the counter). As the defender, the Russians have the option to not spend any supply in defense, but as this would half its defense strength they’ll happily pay the 1T to defend.

STEP 3: Both sides need to declare the Action Rating which they’ll use in the upcoming combat. In this case, since there’s only one unit per side, the choice is obvious, the German’s AR is 5, while the Russian’s AR is 2. In situations were each side has multiple units involved the choice of which AR to use is entirely up to the players. Generally each side will pick the unit with the highest AR, but since the units supplying their ARs are the first to suffer any step loses sometimes a unit with a lesser AR will be chosen to lead a side’s attack or defense.

STEP 4: The Russian unit is sitting in an open ground hex so there are no terrain choices to make, they’re going to get hit in open terrain. The odds are determined by taking the ratio of the attacker’s combat strength and the defender’s combat strength. The Russians, having paid for its defense in Step 2, have a combat strength of 3. The Germans having used Internal Stocks to pay for its combat also gets to use its full strength and then multiplies it by 2, as it’s a mechanized unit attacking in open terrain[*1]. This gives the Germans initial odds of 2:1 for the attack.

STEP 5: To determine the Dice Roll Modifier we simply subtract the defender’s AR of 2 from the attacker’s AR of 5. In this case the DRM will be +3, which will be applied to both the German’s Surprise and Attack rolls.

STEP 6: The roll for Surprise results in a [2,4] that when modified by the DRM in Step 5 results in a 9. Checking the Surprise table we find that a 9 is sufficient for an Attacker to gain Surprise in an Overrun Attack. If this had been a Ground Combat the modified roll of 9 would not have been enough to gain Attacker Surprise as a 10 is needed in that case. Once surprise has been obtained a single die is rolled to determine the number of column shifts that will be applied. The Germans roll a 3, which shifts the once 2:1 combat in Open terrain to a 5:1 combat in Open terrain.

STEP 7: The Germans now roll two dice to determine the combat result. Again, the DRM from Step 5 will be applied to this roll. The Germans roll a [2,5] which when modified, results in a 10 giving a final result of “Ae4 DL1o2”.

Final position after a successful Overrun.

STEP 8: Both sides now have to execute the above result. For the attacker an “Ae4” result means that any units that participated in the attack and have an AR of 4 or higher may gain Exploit capability. The 13th Recon Battalion’s AR is 5, but since units are not allowed to gain Exploit capability during an Overrun, the result is wasted. The defenders, having suffered a “DL1 o2” must lose one step and then take two options as either step loses or retreats in any combination. Since the 15th Infantry Regiment is a single step unit the loss of one step will be enough to eliminate it and no actions are required to resolve the options.

Having successfully Overrun the defending Russian unit, the Germans must advance into the now vacant hex. In a regular Ground Combat an advance after combat is optional, but in an Overrun the attacking units must advance into a newly vacated hex. Since the overrun cost 3 MPs and the 13th Battalion spent 1 MP to move adjacent in order to Overrun, it has spent all of its available Movement Allowance for this phase and its movement comes to an end. If the unit would have had MPs available after the successful Overrun it may have continued with its movement.

STEP 2: The German HQ is unable to supply the 13th Battalion.
The Russian HQ has a 10MP throw range, easily supplying the 15th Regiment.

The odds of the attack before surprise.
The Terrain row and odds column for the final roll.
The final result after applying the DRM.

Having successfully completed the first stage of the plan to capture the village of Krasnoarmeysk, the next stage is to hammer the 24th Guards through the use of air power. Normally the ability of air power to barrage a target is limited to the various Barrage Segments found in the Sequence of Play. Since the Germans would like to use their air power during the Reaction Phase’s Movement Segment the normal barrage procedure won’t do the job, but fortunately the German air force has been giving Hip Shoot capability in the game specific rules[*2].Hip Shoots allow a single air unit to barrage a target duringtheir side’s various Movement Segments. They also allow a single hex to be barraged multiple times per segment, which is an exception to the normal barrage rules, allowing a side to keep trying until they get the result they want or run out of active units to Hip Shoot with. One downside to Hip Shoots is that since only a single air unit is allowed to participate per Hip Shoot they have to go it alone, without escorts of any type.

The air units to the right of the Air Base are Active.

The village of Krasnoarmeysk lies within the Patrol Zone of the Air Base just south of the Russian 10th Amry HQ, which would make flying an unescorted barrage mission a bit of a risky undertaking. Missions flown within an enemy’s PZ suffer an increased chance of being damaged by Flak as well as the possibility of facing Interception which results in Air Combat. Not wanting to risk their precious Stukas in an unescorted mission, the Germans decide to buzz the Russian Air Base with a flight of Bf.109s to try and neutralize the threat.

A Fighter Sweep is a type of Air Mission that can be executed in the various Movement Segments found in the Sequence of Play. By performing a Fighter Sweep the Germans are hoping to ground the two units of Yak.1s which will allow their Stukas an unmolested run on their Hip Shoot Mission.

The start of the Air Combat.

Round 1 reduces and Aborts the first flight of Yak.1s.

Round 2 Aborts the second flight of Yak.1s as well as the Bf.109s.

First the Germans declare a Fighter Sweep Mission and move their Bf.109s onto the enemy’s Air Base. The Russian Air Base contains two Active Yak.1 units and an Inactive unit of Pe.2s. Since there are active aircraft at the base, Air Combat will result. Before Air Combat begins the defender has the option to voluntarily abort all but one Active air unit by placing those units into Inactive status. The Russians, wanting to keep their Patrol Zone active at all costs, decide to leave both units of Yak.1s active to fight the incoming Germans.

Air Combat is resolved in a series of rounds until one side no longer has any Active Fighters left in the combat. If after a round of Air Combat both sides have only Active air units which are not Fighters, the Air Combat is finished and the Active attacker’s air units go on to complete their mission. Each round begins by both sides selecting a single air unit to fight during the round, two dice are rolled and then modified by subtracting the defender’s Air Combat Rating and then adding the attacker’s. The final modified roll is then referenced on the Air Combat Table and the results are executed. Finally a single die is rolled to determine if the aborted air units suffered a Step Loss during combat.

The choices of which units to have participate in this particular example are irrelevant so the first round sees a unit of Russian Yak.1s facing off against the Bf.109s. Two dice are rolled [1,5], the defender’s Air Combat Rating of 2 is subtracted from the result, and the attacker’s Air Combat Rating of 5 is added giving a final result of 9. The defender must Abort from this combat and a single die is rolled to determine if the Yak.1 unit must lose a step. A 5 is rolled, the Yak.1 counter is flipped to its reduced side and placed under the Air Base to show that it is now Inactive. Round one is over.

Round two and the Russian’s last active unit of Yak.1s goes up against the Bf.109s. At this point the Russians are rethinking their decision to engage the German aircraft, but it’s too late. Once Air Combat is started units are not allowed to voluntarily abort. This time the dice roll is more friendly to the Russians [3,1] which is again modified by subtracting the defender’s Air Combat Rating and adding the attacker’s. The final result is a 7 which means that both air units need to abort. A single die roll is made to determine whether or not both units need to take a step loss. A 3 is rolled and both aircraft escape unharmed. The Yak.1s are placed under their Air Base Inactive, and the Bf.109s fly back to their Air Base and where they become Inactive as well. One thing to note is that even if the Germans had not been Aborted in the final round of Air Combat, they still would have had to become Inactive at the end of the Fighter Sweep mission.

The Fighter Sweep was a success. All Russian air power is now grounded and the Stukas will be able to Hip Shoot with out having to face increased Flak or possible Interceptions attempts.

The situation after a successful German Fighter Sweep.


The village terrain in clear view.

The now reduced Ju.87d.

Just one hex too far!

Now that the threat of Russian air power has been neutralized the Germans decide to send in a unit of Stukas to barrage the 24th Guards Division at village of Krasnoarmeysk. Like any other Air Mission, Hip Shoots start by placing the air unit involved into the mission hex. There are no Active enemy air craft in this hex, so there will be no Air Combat during this mission, but before the Stukas can complete their task they’ll have to face Flak. Flak is resolved with a single roll of two dice to which certain modifiers are either added or subtracted. In this case, thanks to the successful Fighter Sweep, none of the modifiers apply and two dice are rolled to resolve Flak. The Russians get lucky with a [5,6] and the Ju87ds are flipped to show their reduced side.

The Stukas, even though reduced, still get to complete their mission. First the Germans need to determine which column on the Barrage Table to use for the attack and find that with a now reduced Barrage strength of 9 the starting column for the Barrage is on the 8-11 column. Next, column shifts are determined by referencing the Shifts table and it is found that the only one that applies is a 1 column shift to the left due to the Close terrain of the target hex[*3]. The shift to the left gives the Stukas a Barrage on the 5-7 column of the Barrage Table. If the Air Base from which the mission originated had been one hex closer the Germans would have received 1 column shift to the right as well, leaving the final Barrage strength as 8-11. With a roll of [3,2] the Barrage has no effect and with their mission complete the Stukas fly back to their base and become Inactive.

Where other Barrages are limited to one per hex in a single phase, Hip Shoots Missions can be attempted as many times as possible during a phase, and with this in mind the Germans strike out at Krasnoarmeysk once more. Again the air unit is placed in the mission hex and the Russians are much less potent with their Flak this time around rolling well below the needed 11 with [4,2]. The initial Barrage column for the 17 barrage strength Stukas is on the 17-24 column which will once again be shifted once to the left due to the terrain. The Germans get to roll on the 12-16 column for their attack and are successful with a roll of [6,3], which results in a “[1/2]”.

On the Barrage Table a result of “1/2” means that there is 50% chance that the units being attacked would lose a single step. A result of “[1/2]” means the 50% chance applies only in certain situations, air barrage not being one of them, so the final result of the second Hip Shoot is that the 24th Guards Division becomes Disorganized. After having completed a successful Hip Shoot the second unit of Stukas flies back to its base where it becomes Inactive.

The first Hip Shoot Barrage Column.
The second Hip Shoot Barrage Column.
The final results of both Hip Shoot Missions.

The situation after two Hip Shoot Missions.


Units conducting the last Overrun.

Having successfully both cut off Krasnoarmeysk from its supply line and Disorganzing its defenders it’s time to for the Germans to conduct a final Overrun in an attempt to gain control of the village. The last available units for this task are elements of the 13th Panzer Division, including an Organic Truck, all of which are in Reserve Mode. Normally Transport Points are not allowed to be placed in Reserve, but Organic Trucks are the exception. Once release from Reserve these units will be able to move up to half of the Movement Allowance during the Movement Segment of the Reaction Phase.

Having been fueled at the beginning of the phase, the Germans release the entire stack, spend five movement points to move adjacent the 24th Guards Division, and having three movement points left announce their intention to Overrun. Although the Overrunning units are now stacked with the 66th Mechanized and 66th Infantry Regiments, other than stacking considerations, friendly units have no effect on the Overrun procedure.

Moving into position to Overrun

Now that the Germans are in position we’ll follow the same exact procedure as above to to resolve the Overrun.

STEP 1: The defending and attacking hexes are 36.31 and 35.32 respectively.

STEP 2: The Germans have three, one step units attacking at a cost of 1T per step, so a total of 3T is drawn from the dump by the 4th Corps HQ and thrown forward to the Overrunning units (remember, adjacent is close enough). If the units would have been out of the throw range of the HQ, the 1SP on the Organic Truck could have been tapped to pay for the upcoming combat.

The 24th Guards, being a 3 step unit, needs to pay 2T for defense. No matter the number of steps on defense, the maximum cost to defend is 2T. While the 24th is well within the throw range of the 10th Army HQ, a valid supply path is not available due to the Zone of Controls of the 13th Recon Battalion, and the 66th and 93rd Infantry Regiments. Remember that in order for units to project a ZOC they must be in Combat Mode. The Germans actually conducting the Overrun, for example, are in Move Mode and don’t have a ZOC.

The initial Overrun by the Germans is paying off. Already defending at half strength due to being Disorganized, the 24th decides to use Internal Stocks to pay for its combat costs and is marked with a Low Stocks marker.

STEP 3: The 24th Guards must supply their Action Rating for defense, as they’re the only unit in the stack. Their normal Action Rating of 3 is reduced by 1 for being Disorganized. The Germans can choose any three of the Overrunning units to supply their Action Rating for the attack and choose the I/4 Panzer Battalion’s AR of 5[*4].

STEP 4: The Russians are in a village, so Close Terrain applies to the Overrun. Normally the choice of which Terrain type to defend from is pretty straight forward, but there are cases where choosing between having an attacking hex attack across a river or into a city may make a difference. The odds are then determined with the Germans having a total of 8 Combat Strength on the attack and the Russians getting 6.5 (13/2 for being DG) on defense for an initial odds of 1:1 in Close Terrain.

STEP 5: The Dice Roll Modifier will be the German’s AR of 5 minus the Russian’s of 2, for a final DRM of +3.

STEP 6: The Germans roll for Surprise and even with the +3 DRM their roll of [1,3] is not enough to gain surprise, so the attack will be resolved as a 1:1 in Close Terrain.

STEP 7: The Germans now roll two dice to determine the result of their Overrun. A [5,4] is rolled and after applying the +3 the result is “Ao1 DL1o1”.

STEP 8: Both sides need to execute the results and as the Germans have to take an option, their decision can effect what the Russians need to do. If an attacker chooses to take their option as a step loss, then the defenders have to take their option. If an attacker chooses to take their option as a retreat, then the defenders can ignore their option.

The Germans, wanting to cause as much damage as possible to the defenders take their option as a loss and the unit supplying their AR for the attack, the I/4 Panzer Battalion, is destroyed[*5]. The Russians now have to take 1 step less (“DL1”) and have the option (“o1”) to either stand their ground and take another loss, or retreat one hex. Since retreating a Disorganized unit through an enemy’s Zone of Control would result in a step loss anyway, the 24th will hold its ground and take their option as a step loss.

While the German Overrun has failed to accomplish its goal, the defenders of Krasnoarmeysk have been severely weakened and will make a ripe target during the upcoming German Player Turn.

The situation at the end of the Reaction Phase.

Oooops, hit the wrong button and published this before it was fully proof read and can’t figure out how to undo it. Oh well…

[*1]: The ability of a mechanized unit to multiply its strength by 2 in open ground is actually a game specific feature that is determined by that particular game’s Terrain Effects Chart, but since this bonus occurs in every OCS game I’ve played, I’ve included it here.

[*2]: While Hip Shoots themselves are not game specific, the ability of an air force to use them is.

[*3]: The terrain type of a hex is given on a particular game’s Terrain Effects Chart. Village terrain is universally considered Close Terrain.

[*4]: Not the best choice of units as a Panzer Battalion is much more valuable than the weaker Cavalry Unit that could supply the same AR.

[*5]: Normally one would not waste an AR 5 unit in this way when it’s clear the objective would not be met. This is done here strictly for example purposes.

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