Assuming that the attacker was able to travel unnoticed or possibly used something like teleportation, how long would it take the military to arrive for a counteroffensive? If possible, I'd like time estimates along with force strength.

More details for this hypothetical

  • Fast moving advanced military (100k soldiers)
  • Clearly more advanced than most or all nations that are known on earth.
  • All matter of abilities including air, land, and sea (great lakes).
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    $\begingroup$ What kind of attacker? ("The" attacker sounds like terrorism.) $\endgroup$ – RonJohn Sep 5 '18 at 19:06
  • $\begingroup$ @RonJohn My line of thinking was a secretly advanced nation or extra/ultra terrestrial. $\endgroup$ – Chris Sep 5 '18 at 19:07
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    $\begingroup$ How many attackers? What are they attacking with? $\endgroup$ – RonJohn Sep 5 '18 at 19:09
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    $\begingroup$ Welcome to Worldbuilding.SE. We'll need a bit more information about your scenario. How big and severe is the threat? Are we talking a few soldiers? An entire army? What sort of weapons? Tanks? Aircraft? $\endgroup$ – Schwern Sep 5 '18 at 19:10
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    $\begingroup$ What kind of force-strength are we talking? Hundreds or thousands of "Infantry?" Armor? Aircraft? What are they doing? Are they leveling everything in sight? Taking and holding a single building? $\endgroup$ – UIDAlexD Sep 5 '18 at 19:10

Since the term "counter-offensive" was used, I'll assume a sort of Red Dawn scenario (the good one), but with teleportation. A major and superior hostile army of unknown origin suddenly appears in Chicago and begins attacking outward.

The National Response Framework would be activated to coordinate effort. NSPD 51 would also be activated, most of which is classified. An attempt would be made to organize the evacuation of Chicago, but it would likely result in the biggest traffic jam in history.

While the US is prepared for smaller attacks, terrorist attacks, or nuclear attack, it is not prepared for a large, well-equipped hostile land army suddenly appearing simply because there's no way it could happen outside of sci-fi. While there are various forces ready to respond immediately, these small units would not last long against an attack of this scale.

The first organized resistance would be 12,000 officers of the Chicago Police, plus surrounding departments. The governor would activate the Illinois National Guard and ask for help from the Federal government and the surrounding areas. Elements of the Illinois National Guard would arrive soon after, specifically the 178th Infantry Regiment in Chicago itself. The Illinois Air National Guard has no combat units. If things are desperate enough Naval Station Great Lakes, a US Navy training facility, might get involved.

United States Army North is charged with the protection of the United States. The major challenge is not distance, but readiness. Its combat units are not on ready combat status. They would need some time to call in their troops, get their equipment out of storage, come up with transportation and operational plans, and get everything organized for transport. Fortunately transport over land is much simpler to organize than over the ocean and they could probably do it in days rather than weeks. Actually then driving to Chicago is fairly easy due to it being very well connected by road and rail.

The first major combat units available would likely be elements of cavalry, airborne, and Marine units which are more mobile and "expeditionary" in nature. Fortunately for Chicago, none of these units are currently deployed. 10-15 years ago a significant portion of the US military would have been busy in Iraq and Afghanistan.

Elements of the heavier units would arrive in the days and weeks to come. National Guard units would be nationalized into the US Army. Reserve units would also be activated, though they will take weeks to gather their men and equipment and organize, adding some 200,000 more soldiers. Additional units would likely be recalled from overseas taking a month or more.

Meanwhile USAF Air Combat Command would organize its continental air forces. First Air Force is charged with defense of the continental US, plus the Eastern Air Defense Sector. This is primarily Air National Guard (ANG) fighter wings operating F-16 fighter-bombers. The closest are likely...

Heavy bomber units of B-52s and B-1 units have the range to fly directly from their bases around the country as soon as they are ready. All 19 active B-2s are part of the 509th Bomb Wing in nearby Missouri. These expensive and limited assets are unlikely to be committed until there is more information about the threat.

The 24th Air Force would also mobilize for cybersecurity and the 25th for intelligence and recon.

More wings would respond as they organize and tanker assets become available. If the battle goes on long enough aircraft from the Boneyard would be reactivated.

US Navy carriers are normally the US's fire brigades, but no US carriers will be appearing on the Great Lakes. The locks of the Saint Lawrence Seaway can accommodate up to 740 ft, but a Nimitz class carrier is over 1000 ft and the Wasps are over 800. Instead, their ready air wings may be forward deployed on land.

All of the Navy's destroyers, cruisers, and littoral combat ships (except the Independence class which is too fat) could make the trip to provide fire support, intelligence, and anti-air. In addition, Chicago is in range of Tomahawk cruise missiles launched from New York Harbor.

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    $\begingroup$ Under article 5 of the NATO treaty other NATO countries forces would also deploy to add the effort. Canadian troops and air assets the British have Tomahawk capable submarines for example. $\endgroup$ – Sarriesfan Sep 6 '18 at 7:21
  • $\begingroup$ @Sarriesfan That's a very good point, I was just thinking about that last night. I doubt they'd be early responders, things would have to get pretty bad before the US govt to allowed foreign troops and combat aircraft on US soil. $\endgroup$ – Schwern Sep 6 '18 at 16:25

Here is list of various military bases in Illinois:
You can also look up Wisconsin and Indiana, they are very close.

Research what they have, and think about how fast they can get it to Chicago. I'd say give them anywhere from half-hour for limited deployment, and a few hours for rolling out 50% of their gear.

Then search for airbases in the US, and estimate flight time.

Edit: Let's take Naval Station Great Lakes for example https://en.wikipedia.org/wiki/Naval_Station_Great_Lakes Mainly a training facility, with up to 7,000 enrolled at the installation at any time. I'd say they arm at least couple thousands of them with small arms and get them to downtown Chicago on trucks or busses in couple hours, and the rest over several more hours.

In general, I would not expect too many battle-ready troops or heavy weaponry near Chicago. It is surrounded by thousands of miles of friendly land. Any conventional force moving to Chicago will be detected long before it gets there, and US military probably does not expect teleporting enemies.

I am sure there are extensive anti-air and anti-missile capabilities, so if they are useful against your force, they can deployed in minutes.

Edit 2: First response will be National Guard. They have armories in the city: http://www.il.ngb.army.mil/Organizations/Army/Cities/Chicago.aspx
I would not expect heavy armor, but Humvees with their usual weapons are definitely there. They probably have several thousand personnel living in the city, and organizational structure to mobilize them on a short notice. They could use same armories to arm cadets from Naval Academy that I mentioned above, and any other non-combat military personnel in the area.

So expect a few thousand soldiers, with Humvees, in couple hours.

Which might not sound like a lot, but military are really planning for riots or national disasters, not teleporting super-troopers.

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  • $\begingroup$ This was a useful post, but it technically doesn't answer the question. I recommend you pick one base and use it as an example of how to use the info you're providing. $\endgroup$ – JBH Sep 5 '18 at 19:21
  • $\begingroup$ "here is a link, do your research" is not an answer. $\endgroup$ – L.Dutch - Reinstate Monica Sep 5 '18 at 19:21
  • $\begingroup$ don't forget the "used something like teleportation" $\endgroup$ – L.Dutch - Reinstate Monica Sep 5 '18 at 19:40

For an American City in general: Anywhere from minutes to months.

There are aircraft flying over the USA at all times, and with the proper authorization they can blow their load on any unwelcome visitor. I would imagine that the airforce has a very detailed (and very classified) set of documents outlining how and when to do that.

When Islamic terrorists have attacked military bases inside the United States, they have normally been killed in less than an hour.

For a military unit to roll out and start fighting inside the borders of the USA would require approval from either the president or the state governor (each with a clear chain of succession in case they are killed.).

For Chicago: Never.

It has no strategic value. Even for Americans, it is almost ungovernable. You will find many comparisons of Chicago and Baghdad that show Chicago to be the more violent city.

Launching a counter-attack inside of Chicago puts all of its residents at huge risk of collateral damage, so either a lot of American civilians die, or the military fights under restrictive rules of engagement which may render them ineffective.

An invader would need to garrison tens of thousands - perhaps hundreds of thousands of soldiers to control the city. They would have to feed nearly 3 million people on their own supply lines. To break out of Chicago in any direction, they have to cross 1,000 miles of flat, open terrain with the entire might of the USAF bombing them to dust.

tldr: If someone invaded Chicago, we would probably let them keep it.

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    $\begingroup$ Worldbuilding is not for political commentary. $\endgroup$ – Schwern Sep 5 '18 at 19:25
  • $\begingroup$ @Schwern His politics aside he raises an interesting point - Chicago isn't a good place to break out from. Any significant force moving over land would get absolutely slammed by the USAF. Once it's clear that they're fighting an army and not some terrorist cell, containment and preventing further intrusion would be top priority, especially since Chicago isn't a huge strategic asset. $\endgroup$ – UIDAlexD Sep 5 '18 at 19:33
  • $\begingroup$ what, exactly, are my politics? $\endgroup$ – user47242 Sep 5 '18 at 19:36
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    $\begingroup$ Chicago is not a major military asset, but it is important for economy: it is a transport hub (link from Mississipi to Great Lakes), and home to major commodity exchanges that will disrupt banks, manufacturing and farming if they fall. $\endgroup$ – Bald Bear Sep 5 '18 at 19:59
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    $\begingroup$ You forgot to mention the Chicago style pizza... $\endgroup$ – SJuan76 Sep 5 '18 at 21:56

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