Europe - December 2027

The underlying message in your post is that you want warmer weather. I would definitely aim for something around the Mediterranean.

Can I add an option #5 and #6?

Option #5 Istanbul/Turkey. He likes warmer weather, history, eating and drinking well. Istanbul ticks all the boxes.

Option#6 Croatia/Slovenia Lots of interesting sights to see.

History/Military history in particular can encompass campaigns over the last 2000 years. Two ideas: 1) The Dolomites region of Italy was the front between the Austro-Hungarian Empire and Italy in WW I and the front lines there wandered along amazing topography. Italy took the "South Tyrol" from Austria in the peace treaty because they were tired of the Austrians dropping artillery shells onto Cortina d'Ampezzo. Good food too. The Socha River Valley in Slovenia (called the Isonzo Front in Hemingway's A Farewell to Arms was the eastern end of this boundary and has amazing mountains, topography, history, etc. Both easily accessible through Venice. 2) I took three Paris based tours to WW I battlefields in France during 2018, the centennial of the end of WWi of course. There are many tours out of Paris or Brussels to the trench areas. The days will be short (7 hours between sunrise and sunset) in Europe in December. Weather will be a mix of wet and whatever so going somewhere with both indoors and outdoors activities would be best.

I can't imagine he wants to go to Versailles. I'm not sure Giverny is even open in December. I wouldn't want to visit there then regardless. Anything that far north is going to have short days in mid-December, so I would rule out Paris and London.
For such a short trip, I would look for a direct flight to/from your home airport as a starting point.
Portugal?

Forget about Northern Europe.
At a minimum, consider the Mediterranean. The French Riveria is not so wonderful in Winter. Yes, it is warmer than Northern Europe, but it is not really warm.
Suggest a place with history. There is lots of history in the Med.

For Spain, I would recommend the south, Seville, Cordoba, Granada.
A relatively inexpensive place to go loaded with history, REALLY LOADED is Egypt. Tours there are inexpensive and the Pyramids of Giza, wonderful new National Museum in Giza and a Nile cruise between Luxor and Aswan would be wonderful.
Check Gate 1 Travel for options. You would need 10 days there.

Greece is another option.

Hi, for the unpredictable weather you can have plus short daylight, to maximize your time, I would choose bigger cities. I think your option to go to London sounds great. There’s a lot to do indoors. It’s likely a quicker flight or even a direct flight, depending on where you live. That could be beneficial in December since you’re tight on time.

Of your choices, you can’t go wrong with London. It’s got everything, and is the kind of place where you can do your own thing for part of the day and catch up later. While there’s rich sightseeing, there’s also just cool neighborhood stuff that a young person would enjoy, like a street art tour in East End or a jump up to Camden. December is actually a surprisingly busy time in London. This can be fun with everyone out and about with holiday cheer, but can also be a hassle trying to get a table to eat. Weather is generally mild compared to our Midwest freeze though rain is common. 7-10 days is too much for any one town imo, but London is well linked by rail just about everywhere. The younger set I know rave about Bristol, and Bath is on the way, but there’s a whole slew of places to see. Heck you could Eurostar to Paris too. If you do decide on London, book accommodations as soon as possible.

Also, no to Italy??

Italy is certainly an option. We've been to Rome, but he's never been to Assisi, which I love.

I’m always going to recommend London and England. Always.

Military History:
Bletchley Park ( a must see )
Churchill War Rooms
Imperial War Museum
DeHavilland Aircraft Museum in Herfortshire
Imperial War Museum in Duxford
St Ermins Hotel
https://mainlymuseums.com/post/1417/st-ermin-s-museum-hotel/

https://londonist.com/london/things-to-do/second-world-war-london

Fun things in December
Santa Runs
Cablecars
Dining in Igloos
Sunday Roasts
Street Markets where you will find stocking gifts and Xmas Cards
And if shoppers: Spitalfields and Liberty. Harrods if you must.

Pubs:
The Antelope
The Dove in Hammersmith
The Kings Arms on Roupelle Street
The Mayflower in Rotherhite
Skehans Irish Pub
The Victoria Paddington
The Mitre on St Mary’s Grove in Richmond. Great pizza and salads and the best pub dog, Rudi.

I'll throw another option into the mix. Sicily is loaded with history. Since it is located in a strategic place in the Mediterranean, it was invaded and ruled by EVERYBODY at one time or another -- Greeks, Romans, Spanish, Normans, Arabs -- layers and layers of history. For more recent military history, there's a WWII museum in Catania. You won't freeze your faces off; typical December temps are high 50's and low 60's.

The difficulty would be figuring out the right itinerary for the time you have available. We spent 2 weeks there on a OAT (Overseas Adventure Travel) tour. On your own, you would need a car to get the most bang for your buck. Two of my must-sees would be Villa Romana del Casale and the Valley of the Temples (Agrigento), in the middle of the island and probably not easy to get to (in a timely manner) by public transportation. But you would not want a car in Catania or Palermo; way too hard to drive or park.

We prefer to try to go south of the Alps, you could easily have lousy weather further north. The French Riviera can be chilly in December. One thought is leaving on Dec 15th it will be quiet(er) in Europe until Friday, Dec 20th, when kids will be getting out of school & Christmas holidays are starting. So anywhere you'd like to see with fewer crowds, those are the days to try to do it!

He likes history, especially military history, eating and drinking
well, doesn't mind old churches, not an art person.

I will second the idea of Sicily, and yes it really was invaded by everybody. I think it ticks all those boxes! I would suggest just staying in Palermo with day trips - Weather will be warmer, easy to take a day tour to the Greek temples of Agrigento, visit the cathedral of Monreale, & spend a day in Cefalu.

My second idea would be to focus on WW2 sites around Paris, of which there are so many and much is written on the Forum. Good luck!

Reese.....To avoid the grey and/or rainy weather......Istanbul, Sicily (definitely the full 10 days), Spain (Sevilla and Cordoba with Madrid and a day trip to Toledo), Lisbon and Porto Portugal. Or Madrid and Barcelona as you suggest. Definitely go for all 10 days. Are you counting actual tourism days in the 7-10, or are travel days to and from Europe included in the 7-10 days? If they are, then you have 5 to 8 days for the actual visit, so plan accordingly.
Lots of luck in your planning!

What a lovely gift for your son. I will just share based on my experience:

-London in December is not nice, it's very dark and it rains all the time. It's ok if you only plan to do indoor things, but I wouldn't recommend it.

-Paris in December is also constant rain, and not much better weather than here.

-I've not been to the French Riveria in December but I have been in late January, and it's not warm but definitely a bit nicer than here. I'm not sure you'd have a lot of historic sites?

-One year we spent xmas break in Barcelona and the weather was quite nice. I've also been to Madrid in late January and had similar nice weather. For me, this would be my top choice of your options. It will also be less crowded than the warmer months.

Another suggestion I will provide is Rome- I've been in December and January and it's very pleasant. You still need a coat but you're not feeling cold all the time. It's also less crowded than other times of year, and in terms of history, it's pretty difficult to beat. With up to ten days you could also head down to Naples and visit Pompeii/Herculaneum. Good luck with your planning!

Another vote for Sevilla and Granada. The Alhambra, the Albaicín, the restaurants in Granada and the Alcazar, the Sevilla Cathedral, the Archives, Christopher Columbus stories, architecture and tapas bars …. We had amazing weather in December of 2023. Our kids ages 23-33 loved it!

Thats said, we are all headed to London this Christmas so I will fill you in afterwards!

especially military history

Are specific eras or aspects of military history that he want's to see? For example, Spain was neutral in both WW1 & 2 if that is his interest. However, they had a civil war in the 1930's, were the site of many Napoleonic and Medieval era conflicts, and the Romans came, saw, and conquered.

War history, eating and drinking? Prague and Budapest. Or Istanbul and Prague (Turkish Air layover on the way to Prague), or anyplace and Prague.