As many
fine gentlemen before me, I felt the urge to convert OHW’s rules to play them
on a gridded map. My main goal was to be able to play on a much smaller area
than my sausage fingers allow when using free movement, with additional side
benefits including being able to play online/by mail or similar method. Ideally,
I wanted to stay as close as possible to the free movement rules described in
the book – including subtle emergent effects and interactions between troop
types, unit frontage/density, board to movement ratios, ‘road block’ effects etc.
I’ve realized that most OHW scenarios are very
carefully balanced, and messing with any of the above parameters would
unavoidably bias it toward one of the sides… making them much less interesting.
As the title suggests, I’ve only tackled the horse and musket period so far – I
think this is the era in which OHW rules most shine (this will be the subject
of a future post, I think). Without further ado, this is what I’ve come up so
far.
The Board
This was
easy. All OHW scenario maps are 36”x36” squares, divided in nine 12”x12”
sections. Most terrain features are neatly aligned with this grid and span some
multiple of 6” in both directions. In theory, either hexes or squares would work,
but I prefer hexes for everything except ancient pitched battles. I chose hexes
to represent 3” on the map, resulting in a 12x12 square arrangement of hexes.
[Side note:
double-sizing them to 6” would still adequately represent OHW maps, but would
be too coarse to represent some of the finer implications of the movement rules].
Unit representation
Here, the
obvious choice would be to have each unit occupy one hex, but this would
largely underplay the actual size of the units with respect to board size. In
the rules-as-written, artillery must occupy a 2”-4” frontage, while all other
units’ width is specified to be 4”-6”. This is actually important because the
larger the units, the harder it is to concentrate firepower, coordinate attacks
and form an ordered battle line. Since I always like a tactical challenge, I’ve
opted to have all units at maximum size (4” for artillery and 6” for infantry,
skirmishers and cavalry). Due to this, I play with all units occupying two
adjacent hexes. Artillery is admittedly a borderline case, but I’ve found that
having two different unit sizes needed a lot of extra rules overhead for little
benefit – so I’ve accepted a (slight) overestimation of its frontage instead.
Having units span two adjacent hexes also mean that their ‘centre point’ (as
often invoked by the rules) can be univocally defined as the node connecting their
two hexes on the front side.
[Side note:
in the following discussion, when I refer to “part” of a unit I mean “at least
one hex containing the unit”].
Ranges and front arc
Figure 1
shows how to calculate ranges to and from a unit. OHW requires most
measurements to be performed from
centre points (even though it’s often vague about where exactly the target point is, but I’ll discuss this
later). Due to this, a somewhat counterintuitive result is that the only hexes
at a 3” range are those adjacent to both the unit’s hexes. All other adjacent
hexes are considered to be 6” away, then 9”, and so on. No further surprises
here! Front arc can be easily defined as in figure; it’s the closest you can
get to 45° with hexes and I don’t see any better options.
[Side note:
when a scenario specifies that a unit must enter ‘from’ a given point, I play
that the specified point is the front hex at 3” distance and measure movement
consequently].
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Figure 1: centre
point (red dot), front arc (shaded area) and distance of hexes relative to a unit.
Ranges beyond 12” are only needed for artillery shooting. OTOH, artillery range
is so huge (150% of a board edge!) that it’s hardly necessary to actually
measure it… |
Movement
OK, this
was a bit tricky to nail down. In OHW rules-as-written, moving a unit entails
shifting its centre point along a straight line up to their movement allowance;
unrestricted pivoting on the centre point is allowed at the start AND the end
of the move. This creates a series of implications which one may or may not like
(I think they’re kind of OK for horse and musket games); for example, you
cannot go ‘around’ impassable terrain or units in one move; and pivoting at the
end of the move effectively gives you a slight boost in terms of how far some part of the unit can travel in a
move.
Another
aspect to consider is that if you only allow one unit to occupy each hex, you
artificially reducing the maximum density of troops achievable under standard
rules. This is often relevant as several scenarios have units enter from a
specified point such as a road; and maneuvering slow units out of tight spots
can be extremely difficult if stacking is disallowed, resulting in ‘traffic
congestions’ that simply wouldn’t happen with free movement.
To reflect
all this, I define a normal (i.e. non-charge) legal move as a move in which:
1) At least
part of the unit (see above) ends
within its maximum movement allowance.
2) An
unblocked straight path exists between the starting centre point and the final
centre point. A movement straight path is blocked by any part of a hex
(EXCLUDING hexsides and corners) containing terrain the mover cannot enter,
and/or units the mover cannot pass through. In the horse and musket era, this mainly
means that skirmishers ignore other units and woods when moving; and that all
units ignore skirmishers. Only infantry and skirmishers can end their move
being partly in a town; other terrain types work as described in the book,
without hex conversion problems.
3) Exactly
two friendly units can stack in the same hex (or hexes), but only if both have
the same facing. Enemy units can never stack. The relative position of stacking
units counts (i.e. one will be in front of the other; I can’t find the energy
to actually write down rules for this, but it’s quite obvious that one of the
two stacked units will be the only possible target of shooting/charges
depending on the angle of attack).
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Figure 2: examples of
movement. Shaded hexes are those within infantry Unit #1’s 6” movement
allowance. Unit #1 (move = 6”) can move to positions A and B, since they both
result in part of the unit still being within movement range. The moving unit
cannot pass through Unit #2 (so it cannot move to D), but it can still move to
B because the movement straight path only touches the edges of a blocked hex
rather than its interior. Unit #1 can move to C because it ends aligned (i.e. having
the same facing) with Unit #2. It cannot move to E since the movement straight
path touches the interior of an hex containing terrain it cannot pass. |
Charges
In OHW,
charges only differ from normal moves in just two respects: (1) pivoting is
only allowed before moving, and (2) initial pivoting cannot exceed 45°. Point
(1) means that you cannot use that ‘extra pivoting reach’ you usually get as a
side effect of normal moves to contact enemies (that would definitely look
silly). Point (2) can be also rephrased to “you can only charge targets in your
frontal arc”.
A crucial
point is that you actually have to reach your target with a charge! I know it
seems trivial, but most grid adaptations I’ve seen allow melee attacks to be
performed from adjacent hexes, while
still requiring units to fire into
target hexes. However, this messes up OHW unit balance completely: for example,
it would allow horse and musket cavalry to frontally charge infantry and
skirmishers without ever coming under fire, which is impossible in the rules as
written.
Translating
all this to hexes, a legal charge move must comply with these additional
requirements with respect to a normal move:
1) A charge
move must end with the whole unit
within movement range (no extra 'pivoting' range for part of the unit at the
end of the move)!
2) It must
end with at least part of the charging unit in the SAME HEX as part of the
target unit; facing is irrelevant since this does not count as stacking. [Side
note: in the horse and musket rules, this brief occupation of the same hex by
chargers and their targets is immediately resolved after rolling for
casualties, since cavalry will either shatter their target or be repulsed].
3) At least
part of the target unit must be within the charger's front arc at the start of
the charge.
Charges to
the flank and rear are adjudicated based on the target’s front arc: if at least
part of the charging unit lies within the target unit's front arc at the start
of its move, it's a frontal charge. If not, it is a flank/rear charge.
Easy-peasey!
Repulsed cavalry charges
The book is
quite vague about how exactly moving falling back units. I play that a repulsed
cavalry unit must move ‘back’ to a position (1) fully within its original front
arc, and (2) within 6” of the target hex.
[Side note:
due to how charging and falling back work, I’ve found it’s much easier to just
declare a charge without actually moving the cavalry unit, adjudicating its
final position only after the charge’s outcome is known].
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Figure 3: examples of
charging. Cavalry Unit #5 can charge enemy infantry unit #1 since it can reach
a hex containing part of it with a legal move fully ending within its 12” movement
allowance (shaded area). It cannot charge Units #2 and #3 because the straight
movement paths are obstructed by terrain (#2) or units (#3) it cannot pass
through. An unobstructed straight movement path exists to Unit #4 (it only
touches the corner of one hex occupied by cavalry Unit #6); however, the target
unit cannot be reached with a legal charge move since it fully lies outside the
cavalry’s 12” charge range. Unit #1 will count as attacked in the flank/rear; charges
towards all other units would have counted as frontal (if they could be
reached, that is). |
Shooting
In addition
to being stationary as per standard OHW rules, a shooter can inflict losses on
a target unit if all of the following is true:
1) At least
part of the target unit must lie within the shooter’s frontal arc AND shooting range.
2) An
unblocked shooting straight path (aka LOS) must exist between the shooter's
centre point and the target's centre point. LOS is blocked by any part of a hex
(EXCLUDING hexsides and corners) containing enemy units other than the target,
friendly units, and 'area' LOS-blocking terrain (woods, towns etc). LOS extends
into (or out of) one such hex, but no further. Hills have a central crest which
runs along hex sides; LOS is only blocked if it crosses the crest.
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Figure 4: shooting
examples. Infantry unit Blue#1 has not moved, and has as many as four enemy
units at least partly within its front arc! However, it quickly realizes it cannot
shoot Red#1, since it’s fully outside musket (12”) range. Red#2 and Red #4 are
within shooting range, but neither can be shot since LOS is obstructed by a hex
containing an enemy (#2) or friendly (#4) unit. A somewhat irritated musket staccato can be heard as Blue#1 begins shooting
its only available target, Red#3. |
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Figure 5: more
shooting examples (terrain and LOS). Again, Blue#1 is apparently spoilt for
choice with regard to possible targets. Skirmisher unit Red#9 can be targeted (at
half effect) since part of it is within front arc and range; LOS extends into the first met obstructing terrain hex.
However, it cannot extend out of such
a hex; due to this, LOS to Red#2 is obstructed. View of Red#3 is completely
obstructed by the hill (LOS is blocked by the highlighted hill crest hexsides).
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I’ve used
these rules for several OHW horse and musket games without any particular
problem – I think they work just fine. The first scenario I’ve tried with hexes
was the excellent No.8 “Mêlée”, and it resulted to be extremely balanced through multiple replays – a good indication
that no bias was introduced by ‘hexing’. Encouraged, I continued with other
scenarios. I’ll post about this soon.
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Figure 6 - OHW scenario #8 converted to hexes with terrain annotations - useful to get players on the same page prior to battle!
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