Hellsing Volume 1

The manga ran for eleven years, from 1997 up to 2008 (Wikipedia).

Out of all Hirano's series only "Hellsing" was released worldwide: in North America, Australia, New Zealand, France, Germany, England (Wikipedia).

Many Hellsing characters, or their prototypes, appered in Hirano's earlier works (Alexander Anderson, the Captain, Bernadotte, Integra, Yumiko/Yumie) (Wikipedia).

Hirano has admitted he drew inspiration for Alucard's appearance off of Vash the Stampede from the manga and anime series Trigun (notice the similar coat and glasses). This is most notable in Volume 1, when Alucard's art design was vastly different from the rest of the Manga (link)

"Alucard" is "Dracula" spelt backwards

Alucard was tamed by Abraham Van Hellsing. The name is taken from Bram Stoker's novel, "Dracula".

"The Bird of Hermes is my name, eating my wings to make me tame" is a line from the Ripley Scroll, a 15th centure alchemy treatise.

The physical model for Father Anderson seems to be Edward Van Sloan, the actor who played Van Hellsing in the Bela Lugosi version of the film Dracula. This includes his short thinning hair, facial structure, and small circular glasses (link).

Maxwell and Schroedinger's names probably come from the famous scientific experiments of James Clerk Maxwell and Erwin Schroedinger.

Rip Van Winle's name is taken from Washington Irving's novel.

In several scenes Rip Van Winkle is seen with an umbrella, which could be a reference to the practice of World War II German snipers to use umbrellas with camouflage foliage woven between the arms as light, adaptable and mobile personal camouflage (link)

Integra Hellsing uses Walther PPK and .455 Webley (link).

Firearm cartridge .454 Casull's caliber is 11,5 mm, not 13 (link).

Alucard's Jackal is probably a modified Gyrojet pistol (link).

During WWII Alucard uses Thompson Model 1928 (link).

Seras uses MG-42 machine guns against the Captain (link).

The Harkonnen cannon Walter equips Seras Victoria with was named for the evil Baron Harkonnen, from Frank Herbert's novel 'Dune'. This is evidenced in the manga, as the "Spirit of the Harkonnen" appears in a dream sequence as, indeed, the villain from the David Lynch movie, Dune (IMDb).

Bernadotte uses AK-74 (link).

The Wild Geese use AK-74 и CAR-15 ((link).

Heinkel Wolfe uses The Dragunov sniper rifle against Walter (link).

The Major uses Walther P38 (link).

The Captain uses modified Mauser C-96 (link).

Millennium vampires use StG 44, Panzerschrecks, Panzerfausts and MG-42 (link).

While in Brazil (vol 3) Alucard stayed is Copacabana palace (link).

The plane from chapter 31 (vol 5) is Lockheed SR-71 Blackbird (link).

Hellsing is written and drawn by Kouta Hirano. The manga series began in 1997, and ended in September, 2008. The series ran for 95 chapters, 10 completed volumes and a little over 10 years.
The manga, produced in black-and-white, has an interesting art style with strong lines and contrasting inked areas. The story has a straightforward plotline, weighted towards action and horror scenes, but with a sprinkling of humor in both the writing and art.
Kouta Hirano has created two companion series that are related to Hellsing. Crossfire is not Hellsing canon, and is not set in the Hellsing universe, but it does feature an alternate version of Iscariot where Heinkel and Yumie figure as main characters. The Dawn, on the other hand, is a canon prequel to Hellsing and does take place in the Hellsing universe. It is set during World War II, where Integra Hellsing's father is alive and running things, Alucard has apparently chosen to take on the form of a young girl, and Walter Dorneaz is a cocky teenager.

Hellsing is named after and centered around the Holy Order of Protestant Knights, originally led by Abraham Van Helsing. The mission of Hellsing is to protect Queen and Country from the undead and other supernatural forces of evil. This organization is currently led by Sir Integra Fairbrook Wingates Hellsing, who inherited the leadership of Hellsing as a child after the death of her father. She is protected by the faithful Hellsing family butler and former Hellsing "trashman," Walter C. Dornez, and Alucard, the original and most powerful vampire that swore loyalty to the Hellsing family after being defeated by Van Helsing one hundred years before the story takes place. These formidable guardians are joined early on in the storyline by former police officer Seras Victoria, whom Alucard turned into a vampire.
As the scale and frequency of incidents involving the undead escalate in England and all around the world, Sir Integra discovers that the remnants of a Nazi group called Millennium still exist and are intent on reviving the Third Reich by creating a battalion of vampires. Millennium, Hellsing, and the Vatican section XIII Iscariot clash in an apocalyptic three-sided war in London, and Millennium reveals its true objective: to destroy the vampire Alucard, ending a feud begun during World War II.

Wikipedia

An anime series of the same name was produced by Gonzo. Directed by Umanosuke Iida, the series was based on the manga, but used a screenplay by Chiaki Konaka and is significantly different from the manga in terms of plot, though it uses some of the same characters and similar character designs. Spanning 13 episodes, it was broadcast on Japan's Fuji Television from October 10, 2001 to January 16, 2002.

An original video animation (OVA) entitled Hellsing Ultimate is being produced by Satelight and Geneon. It follows the manga storyline more closely than the anime series.[1] The first episode was released in Japan on February 10, 2006, and as of December 2009, seven episodes have been released. The sixth OVA in the series will be available on both DVD and Blu-Ray, with Blu-Ray editions of episodes one through five were out on October 22, 2010 in Japan.[2] The first episode was released in North America on December 5, 2006. As of August 2010, four episodes of the OVA have been released in North America. At Anime Expo 2010 Funimation Entertainment announced that they have licensed three of the new OVA episodes 5-7 and the original TV series and these will be released in the USA in 2011.

Wikipedia