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Today in Alternate History
Day in Alternate History Blog
Civil War Sealion: The Capture of Washington, D.C.
At alternatehistory.com, the term "Sealion" has become a watchword for a
commonly-known, but extremely unlikely alternate history. Virtually everyone
familiar with the history of the Second World War knows about Hitler's plans for
the invasion of England, and almost as many people know about the problems that
would plague any invasion — the lack of effective transport, insufficient
training for the landing force, the continuing resistance of the RAF, and the
undimmed might of the Royal Navy. All these factors combined to foil the
invasion. On the surface, a successful invasion seems likely, but as we examine
the facts, the truth comes out — it simply wasn't possible. Events like these
are "Sealion moments." On the surface, they appear plausible, but as we look
deeper, the impracticality of the plan becomes apparent.
The American Civil War is no more immune to Sealion moments than is the Second
World War. One instance in particular stands out — the capture of Washington,
D.C. by the Confederate Army of Northern Virginia. Despite innumerable books and
short stories describing the fall of Washington, at no time during the course of
the war was the Army of Northern Virginia in position to capture the Union
capital. Insufficient forces, a shaky logistical train, Union defenses, and the
ever-present threat of the Army of the Potomac made it impossible for the
Confederacy to have ever captured Washington during the war.
In 1863, just two years after the fall of Fort Sumter, Washington boasted over
60 forts and 93 batteries containing 837 guns manned by 25,000 men. The defenses
of Washington contained more artillery than the combined total of the Army of
the Potomac and the opposing Army of Northern Virginia. 13 miles of trenches
supported the forts, which were arranged in a then-unique supporting structure.
Rather than standing alone, the forts of Washington contributed to each others'
defense, and were positioned so they could cover the dead spots in their
neighbors' fields of fire. This was technique used in the lines of Torres Vedras
by Wellington to protect Lisbon from French forces during the Napoleonic Wars.
Fifty years of progress later, Washington could be declared the best-defended
city in the world. Until the trenches of the First World War were dug, no
fortification system in the world even came close to the interlocking system of
defense that protected Washington.
With a massive ring of forts protecting the city and constantly manned by Union
troops, taking the city in a lightning stroke would be impossible. A
contemporary army would be forced to besiege, batter, and wear their way through
the defenses in a costly, months-long (if not years) campaign. During that time,
the attacking army would be vulnerable to the Union Army outside the defenses,
while the city's defenders would continue to receive supplies via the Potomac
River. The entire perimeter of the defenses was 37 miles, meaning that an
attacking army would be required to guard that entire distance. The sheer
logistics of a siege make it impossible for the Confederacy to even attempt.
Of course, if you have a Point of Departure prior to the beginning of the war or
even posit the intervention of Alien Space Bats, all these arguments go out the
window. The best instance of this is in Harry Turtledove's Guns of the South, in
which Confederate forces armed with AK-47s are able to overrun the Washington
defenses to capture the city. Even this scenario, however, has its problems —
Turtledove conveniently overlooks the existence of two additional bridges across
the Potomac (Long Bridge is listed as destroyed in the text) that would have
allowed Grant's forces to reinforce the city and prevent its capture. Even with
weaponry nearly a century more advanced, the capture of Washington in GoTS is a
In our timeline, of course, the Confederate Army of Northern Virginia did not
have AK-47s. Indeed, until the capture of the Federal arsenal at Harper's Ferry
in 1862, there weren't enough rifled muskets to arm the entire Confederate force
with the most modern weapons. The shortage of weapons wasn't limited to
individual rifles — the Confederacy had a severe lack of artillery as well. In
1861, more guns were produced in the state of New York alone than in the entire
Confederacy. This lack of heavy artillery would hamper Confederate armies at
every turn, and if the Army of Northern Virginia had attempted to capture
Washington, this lack would have been a massive disadvantage in a lengthy siege.
During the entire course of the war, Washington came under direct, large-scale
attack only once. In July 1864, 20,000 Confederate soldiers under the command of
General Jubal Early snuck across the Potomac and attacked the northwestern
defenses of the city in an effort to distract U.S. Grant from his attack against
Richmond. After trying to force the defenses for two days, Early's force
retreated. Confederate forces never even reached the walls of Fort Stevens, the
main fort under attack.
Though this was one isolated event, the Army of Northern Virginia did have
chances to attack the capital. In every instance, it chose not to do so —
deterred, no doubt, by the city’s defenses. Three main opportunities stand out:
in the wake of the Battle of Bull Run, during Lee's Maryland invasion, and
during what would become known as the Gettysburg Campaign.
Let’s address these one at a time, and discuss why Washington would not have
fallen, even had the Confederacy attacked at that time.
The Battle of Bull Run
Even before the Battle of Bull Run, work had begun on the defenses of
Washington, D.C. Initial barricades had been prepared within the city, and in
May, work began on forts to protect the Virginia ends of the Aqueduct Bridge and
Long Bridge. These works were expanded in the seven weeks between the time Union
troops marched into Virginia and the Battle of Bull Run. More than half a dozen
forts and batteries sprang up along the banks of the Potomac. They were small,
independent works intended to defend the bridges across the river, and didn’t
constitute a self-supporting defensive line, but they were a start.
The work was interrupted by the Battle of Bull Run. Engineers working on the
fortifications were swept south with the Army of Northeast Virginia. In the wake
of the disastrous battle, Washington was terrified by the fear that the
Confederate Army was about to sweep down upon the city. Contemporary newspaper
accounts reveal wild rumors of Confederate forces advancing on the city, of
Confederate cavalry crossing the Potomac to strike at the city’s undefended
rear, and of Confederate supporters rising up across Maryland.
We now know that the Confederate forces involved in the first major battle of
the Civil War were in no condition to conduct a pursuit of the disorganized
Union troops. The initial stages of the battle had badly shaken the Confederate
regiments, and only the intervention of Gen. Jackson's Virginians prevented a
Confederate defeat. From a force of 33,000 at the beginning of the battle, the
Confederates could muster fewer than 30,000 troops in still-green regiments.
Most of the losses came from desertions. Fewer than five hundred confirmed dead
are recorded on each side, a judgment on the inexperience of each side.
But what if the Confederate forces had engaged in a pursuit immediately after
the battle? The short answer is that they couldn't. This was the first battle
the soldiers had fought in, and many were suffering from what would later become
known as post-traumatic stress disorder. In addition, the companies and
regiments involved in the fighting had become disorganized. Any immediate
pursuit would have resulted in a Confederate force no more coherent than the
Union men they were chasing. Any exhausted Confederates arriving at Washington
in fighting order would then face the Potomac forts and a handful of fresh
(though green) regiments bivouacked in and near the city, in addition to
whatever veterans of the battle had managed to reform.
But what if the Confederates had regrouped first? That would avoid the problems
of exhaustion, and would allow time to regroup. It would also open up a host of
other problems for the attackers.
They'd be facing a new Union commander — General George McClellan, who assumed
command six days after the battle — and a new series of earthworks, which
McClellan had ordered in the first days after assuming command. The Union forces
would've had time to regroup as well, and would have been bolstered by fresh
regiments brought in by train from the north. The new Army of the Potomac that
replaced the Army of Northeast Virginia was stronger and more experienced than
But the odds would be far better than those later in the war. An advance on
Washington in August or September would have been the Confederates' best chance
to capture Washington. This period in time was similar to what would be
experienced by Great Britain in the summer of 1940. By Christmas 1861, the forts
begun by General McClellan were finished, so any successful attack on the city
would have had to have taken place before that date. The Confederates would have
had the momentum provided by victory at Bull Run, better (though not good — the
Union would still have several thousand more troops available) odds, and would
avoid the need to break through the massive defenses built later.
But they would be facing General George McClellan, entrenched with upwards of
30,000 men in the Arlington hills. Today, McClellan is derided as a sluggard —
someone who couldn't move quickly, who didn't take advantage of his numerical
superiority, and who was never fully happy with his logistics. In a fight for
Washington, all of his disadvantages would have been nullified. He would be
facing an enemy that was coming directly to him — there would be no need to hunt
for the Confederate force and would have no chance to be slow in moving to meet
the opposition. He would be fighting from a prepared defensive position, not out
in the open field. And he would be fighting with the entire might of the Army of
the Potomac, an army that would know that it was the last line of defense
between the Confederacy and their nation’s capital city.
The situation might be likened to that of General Bernard Law Montgomery in the
Battle of El Alemein. Like McClellan, Montgomery was cautious, liked to
stockpile men and equipment before an offensive — often to excess, according to
each man's detractors. Like El Alemein, the Battle for Washington would be a
set-piece battle, working to McClellan's strong suit. There would be no need to
maneuver, no need to execute complex orders in order to bring all of his men
into battle. And like Montgomery’s men at El Alemein, McClellan’s men would go
into the fight knowing that they couldn’t easily retreat from this fight. As
commander of a battle for Washington, McClellan would do as well, if not better
than, any general in the Union Army, including Ulysses S. Grant.
An attack against Washington in the fall of 1861 would still be a ferocious
fight. But it would be a Union victory. Fighting from prepared positions, with
greater numbers of soldiers and artillery, and with a firm supply line, it would
be a massive victory for the North. It would completely shift the momentum of
the early months of the war, and might deal a death blow to the nascent
Confederacy. With their largest army destroyed, it would be difficult to
continue the fight against the already numerically-superior Union.
In the end, the Confederate leaders could see exactly what I've just laid out
here. They did not attack Washington for those very reasons — to do so would to
play into the hands of the North. It was a risk not worth taking. And after all,
their war was a primarily defensive one. The South could win simply by
continuing to exist. It did not need to take Washington to win. It was the North
that had to go on the attack, which it did with the Peninsula Campaign during
the spring of 1862. That campaign would in turn spark the next chance for the
Confederacy to attack Washington — The 1862 Maryland Campaign.
The Maryland Campaign
In the fall of 1862, the Army of Northern Virginia, commanded by Gen. Robert E.
Lee, crossed the Potomac and invaded Maryland. The invasion had many purposes,
the most important of which was to attempt to recreate the 1777 Battle of
Saratoga, which had brought France into alliance with the new United States.
Jefferson Davis and General Lee both hoped that a major victory on Union soil
would bring France and Great Britain into the war on the side of the
Confederacy. Barring that, Lee hoped to cut the Baltimore and Ohio Railroad,
which supplied Washington and Baltimore. In the process, he might succeed in
spurring Confederate sympathizers in Maryland to make more overt efforts against
In OTL, that wasn't to be, thanks to the interception of Lee's General Order
191, which allowed McClellan to force Lee into battle at Antietam. The result
was the bloodiest single day of fighting in the entire American Civil War and
forced Lee's forces south, back across the Potomac.
So what happens if Lee's Lost Order isn't lost? Harry Turtledove's Southern
Victory Series (Timeline 191) provides one possible answer. According to the
introduction of How Few Remain, Lee would have continued north and east,
eventually meeting the Federal army in combat somewhere in Pennsylvania. Thanks
to the inept generalship of McClellan, the Union army would have been defeated
and the Confederates could have continued onward to Philadelphia, or so goes the
In that story, Lee chooses not to attack Washington, but instead goes for the
comparatively undefended Philadelphia, discouraged from attacking Washington
thanks to that city's defenses. It’s a scenario that makes sense — Lee wanted no
part of attacking the heavily-defended city of Washington. But let's imagine
that Lee believes he can take Washington in the wake of a successful Antietam.
After all, marching on Harrisburg, Philadelphia, or Baltimore would extend Lee's
supply lines possibly beyond the breaking point and leave him vulnerable to
Moving south after the Antietam-like battle, Lee would have faced a hostile
countryside and scattered Union units determined to bring him to battle and slow
his army's progress. 1861 Baltimore riots notwithstanding, the vast majority of
Marylanders were staunch Unionists, and in OTL's campaign, Lee had to forcibly
requisition much of his army's supplies. This would be the case in this scenario
as well. The end result is that his progress will be slowed, allowing for the
Union Army of the Potomac, which would have retreated east or south, to regroup
and resume the pursuit.
If Lee chooses to attack Washington in this scenario, he will do so against a
defensive presence that is fully aware and ready to meet him. In OTL's Battle of
Antietam, Lee could muster 45,000 troops. If we imagine 10,000 casualties at our
Antietam-like battle, that would leave approximately 35,000 able-bodied fighters
to face Washington, a city with 25,000 dedicated defenders. Add in the
5,000-15,000 Union army soldiers present in the city but not assigned to it, and
Lee will be facing between 30,000 and 40,000 entrenched, forewarned soldiers
defending their capital city.
This will not be a surprise attack as was 1864's Battle of Fort Stevens. The
defenders will be alert, waiting, and have numbers equal to or greater than
those of Lee's forces. In addition, the Union Army will still have nearly double
Lee's strength (imagining 20,000 casualties from the Antietam-like battle) with
over 70,000 men. They will be somewhat demoralized, and will no doubt have a new
commander following McClellan's defeat, (in OTL, he was replaced in November)
but after they regroup, they will be a force to be reckoned with, particularly
if Lee is involved in a lengthy struggle to capture Washington.
At the time, the rule of thumb taught at West Point was that an attacking force
should have double or more the strength of the defending force in order to
successfully attack and hold a position. It wasn’t a hard and fast rule, but
it’s an example of the type of thinking that went on during the war. In this
case, Lee would be going up against a heavily-fortified position occupied by
numbers equal to or greater than his own. For all his expert generalship, even
Robert E. Lee would be hard-pressed to outflank a circle.
In order to capture Washington in the 1862 Maryland Campaign, Lee would have had
to meet and defeat the Union army in an Antietam-like battle, advance south
(though the cities of Harrisburg and Baltimore are virtually undefended), break
through the massive defenses protecting Washington, and defeat the ~35,000
defenders of Washington, all before the onset of winter, scarcely two months
away. Lee would have to defeat over 120,000 men in two battles, with fewer than
45,000 of his own men.
Equating the situation to that of Operation Sealion conjures up a picture of
German forces invading England in October, in the face of the Royal Navy and bad
weather, and defeating a British Army that consists of an experienced army that
encompasses over a million men. That’s the scenario, proportionally, that faces
Lee if he attempts to attack Washington in the fall of 1862.
When he fails in his attempt to capture the city, Lee would be forced back
across the Potomac, much as he did in OTL after the Battle of Antietam. The
victory at Washington would then allow Lincoln to issue the Emancipation
Proclamation, which would put an end to any thoughts of European involvement,
particularly in light of Lee's failure to capture a major city like Washington
or Baltimore. The Union victory would be an enormous morale booster and would
virtually cement the position of the Union general in charge. It would also
nullify any chance for Lee to make his 1863 Pennsylvania campaign, a march that
concluded with the Battle of Gettysburg.
Lee's final opportunity to take Washington would be in the wake of a victory at
the Battle of Gettysburg. If Lee could somehow win at Gettysburg without taking
overwhelming casualties (no small feat in itself), the door might be open for an
advance on Washington — but even that would be an impossible task.
William Forschen does an excellent job with this particular scenario in his
recent AH Gettysburg three-book series. In the first book of the series, he
details a Confederate victory at the Battle of Gettysburg, followed by a
Confederate advance on Washington. Lee attacks Fort Stevens in an attempt to
capture Washington, and is bloodily repulsed. It's a fantastic sequence of
events, and very well-written. Lee eventually goes off to take Baltimore before
facing Ulysses S. Grant in a climactic battle.
Many of the problems that face Lee in the 1862 scenario are still present in the
post-Gettysburg campaign. Any prolonged attempt to take Washington brings the
threat that the Army of the Potomac will regroup and take Lee in the rear. The
defenses of Washington are simply too strong to take in a single quick stroke,
and with the threat of the Army of the Potomac, Lee cannot afford to be pinned
down in a protracted campaign for the city. If he hurts the Army of the Potomac
badly enough, a city like Baltimore might be open to his troops, (a la
Forschen’s scenario) but not Washington — it's simply too well defended.
By the summer of 1863, General John Gross Barnard, the chief engineer of
Washington’s defenses, has had two full years to construct every defense that
the industrial capacity of the United States can devise. There are emplacements
for over 1,000 guns, and over 800 of those are already filled with massive
stationary cannon larger than anything available to a field army. In addition,
there are rifle pits, trenches, blockhouses, and bomb-proofs galore for the
20,000+ men of the Washington garrison. Whatever Confederates survive their
victory at Gettysburg will soon face a storm of lead and iron from Washington’s
Throughout the war, the defenses of Washington never stopped growing. New
blockhouses were built monthly, and forts popped up wherever there was a dead
spot in the terrain. In April 1865, even when it was clear that the Confederacy
couldn't threaten the city, two new blockhouses were constructed, and at the
time of Lee's surrender, four more were being built. Forts were under constant
remodeling and expansion from the time they were constructed to the time of the
armistice. New magazines and bombproofs were constructed seasonally, and
training was perpetual.
In addition, the threat of the Army of the Potomac was an ever-ready knife to be
stabbed in the back of any attacker. Even if the Confederates defeat the Army of
the Potomac at Gettysburg, the time needed to break the defenses of Washington
would allow that elastic force to rebound from defeat, just as it did after half
a dozen other defeats at the hands of generals like Lee and Longstreet. Then, an
attacking army would be stuck between the rock of Washington and the hard place
of the Army of the Potomac.
The logistical and manpower problems that face the Confederates form the third
problem facing any attack on Washington. Even if the Army of the Potomac is
defeated, it will inflict heavy casualties on the opposition. The South does not
have an unlimited supply of soldiers or equipment, and if the battle is costly
enough, an attack on Washington may very well be impossible given the numbers
involved. At the battle of Gettysburg, the Army of Northern Virginia could
muster just under 72,000 troops. It suffered roughly 23,000 casualties in that
fight, as did the Union Army, which was in a defensive position. Attempting to
take Washington so soon after even an alternate Gettysburg could well mean the
complete collapse of the Army of Northern Virginia. Unlike the Union Army, which
could draw upon the enormous population of the North, the South could not afford
the loss of the Army of Northern Virginia, and that's exactly what would happen
if the Confederacy attempted to take Washington at any of these three points.
Any attempt to take Washington would end just as Operation Sealion would have
ended — with the attackers going home in caskets — if they went home at all. At
no point in the war did the Confederacy have the ability to capture Washington.
Numbers, fortifications, and logistics all would work against the Army of
Northern Virginia, and its one advantage — that of superior generals — would be
nullified by a force that does not need to scout or move to defeat its enemy.
The German military lacked sea transport; the Confederates lacked heavy
artillery. The Germans faced the English Channel; the Confederates faced the
defenses of Washington. Each had one best moment, but regardless of whether the
calendar read July 1861 or July 1940, the issue was never in doubt.
Eicher, David J., The Longest Night: A Military History of the Civil War, Simon
& Schuster, 2001
Hankinson, Alan, First Bull Run 1861: The South's First Victory, Osprey Campaign
Series #10, Osprey Publishing, 1991
Hoehling, Mary, Thaddeus Lowe, America's One-Man Air Corps, Julian Messner,
Inc., New York, N. Y., 1958.