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Turtledove, Harry. Worldwar: In the Balance. Ballantine/Del Rey 1994 (cover art by Bob Eggleton).

Turtledove, Harry. Worldwar & Colonization
Divergence: 1942 CE
What if: A space alien invasion force arrived on Earth in late May 1942.
Series note: Eight related volumes, comprising either one large series or else two connected smaller series and an epilogue, depending on how you count. Begins with the Worldwar tetralogy, including In the Balance, Tilting the Balance, Upsetting the Balance, and Striking the Balance. Set 20 years later is the Colonization trilogy, including Second Contact, Down to Earth, and Aftershocks. The epilogue is Homeward Bound.

Turtledove, Harry. Worldwar
Series note: Initial tetralogy of the Worldwar & Colonization sequence. Includes In the Balance, Tilting the Balance, Upsetting the Balance, and Striking the Balance.
Original in: English.
Translation: Italian of complete tetralogy by Gianluigi Zuddas as Worldwar: La seconda guerra mondiale che non si èg mai combattuta, Nord 1997 (8842909882).
Awards: Honorable mention: 1996 Sidewise Award for best long-form alternate history.

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Turtledove, Harry. Worldwar: In the Balance. Translated to the Russian as Flot vtorshcheniya (vol. 1), Machaon 2001.

Turtledove, Harry. Worldwar: In the Balance
Divergence: 1942 CE
Summary: Surprised to find Earth's technology so advanced after a reconnaisance probe visited 800 years before, the lizard-like aliens still invade, forcing odd alliances between enemies.
Series note: Volume one of Worldwar.
Published: Ballantine/Del Rey 1994 (0345382412BUY), 1995 (0345388526BUY); SFBC 1994; Hodder & Stoughton 1994 (0340624906); New English Library 1994 (0340618396).
Original in: English.
Translation: Italian by Gianluigi Zuddas as Invasione: anno zero, Nord 1995 (8842908738), TEA 2004.
Translation: Polish by Antoni S. Kowal as Wojna swiatow: w rownowadze, Wydawnictwo Amber 1997.
Translation: Russian as Flot vtorshcheniya, Machaon 2001 (in two volumes).

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Turtledove, Harry. Worldwar: Tilting the Balance. Ballantine/Del Rey 1995 (cover art by Stan Watts).

Turtledove, Harry. Worldwar: Tilting the Balance
Divergence: 1942 CE
Summary: The fight rages on into 1943, with beleaguered humanity pushing harder to exploit captured uranium.
Series note: Volume two of Worldwar.
Published: Ballantine/Del Rey 1995 (0345389972BUY), 1996 (0345389980BUY); Hodder & Stoughton 1995 (0340632399); SFBC 1995; New English Library 1995 (0340648996).
Original in: English.
Translation: Italian by Gianluigi Zuddas as Invasione: fase seconda, Nord 1996 (8842909319), TEA 2004.
Translation: Russian as Otvetnii chdar, Machaon 2003.

Turtledove, Harry. Worldwar: Upsetting the Balance
Divergence: 1942 CE
Summary: 1943 comes to a close with humanity slowly gaining ground against the Lizards after several nuclear exchanges.
Series note: Volume three of Worldwar.
Published: Ballantine/Del Rey 1996 (0345402219BUY), 1996 (0345402405BUY); Hodder ∧ Stoughton 1996 (0340666978); SFBC 1996; New English Library 1996 (0340666986).
Original in: English.
Translation: Italian by Gianluigi Zuddas as Invasione: atto terzo, Nord 1996 (884290953X), TEA 2004.

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Turtledove, Harry. Worldwar: Striking the Balance. Ballantine/Del Rey 1996 (cover art by Stan Watts).

Turtledove, Harry. Worldwar: Striking the Balance
Divergence: 1942 CE
Summary: The war between humans and Lizards slowly culminates in a series of negotiated peaces.
Series note: Volume four of Worldwar.
Published: Ballantine/Del Rey 1996 (0345405501BUY), 1997 (0345412087BUY); Hodder & Stoughton 1996 (0340684909); SFBC 1997; New English Library 1997 (0340684917).
Original in: English.
Translation: Italian by Gianluigi Zuddas as Invasione: atto finale, Nord 1997 (8842909734).

Turtledove, Harry. Colonization
Divergence: 1942 CE
Summary: Twenty years after the Lizard invasion force attacked Earth, the colonization fleet arrives.
Series note: A three-volume sequel to the story begun in Worldwar, and making up the fifth through seventh volumes of Worldwar & Colonization. Includes Colonization: Second Contact, Colonization: Down to Earth, and Colonization: Aftershocks.

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Turtledove, Harry. Colonisation: Second Contact. Hodder & Stoughton 1999 (cover art by Fred Gambino).

Turtledove, Harry. Colonization: Second Contact
Divergence: 1942 CE
Summary: The Lizard colonization fleet arrives at Earth in 1961 and finds it only partially subjugated. Despite a sneak attack on the fleet, colonization begins and runs into trouble when it is discovered that a common herb radically alters the Lizard reproductive cycle.
Series note: First volume of Colonization, or fifth of Worldwar & Colonization.
Published: Ballantine/Del Rey 1999 (0345430190BUY), 2000 (0345430220BUY).
Published: As Colonisation: Second Contact, Hodder & Stoughton 1999 (0340751436); New English Library 2000 (0340751444).
Original in: English.
Translation: Italian by Carlo Boriello as Colonizzazione: Fase 1, Fanucci 1999 (8834706366), 2002.

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Turtledove, Harry. Colonization: Down to Earth. Ballantine/Del Rey 2000.

Turtledove, Harry. Colonization: Down to Earth
Divergence: 1942 CE
Summary: A year of Lizards and humans slowly adjusting to each other instead ends in confusion when the death of Reichführer Himmler leads to returned Nazi designs on Lizard-occupied Polish territory.
Series note: Second volume of Colonization, or sixth of Worldwar & Colonization.
Published: Ballantine/Del Rey 2000 (0345430204BUY), 2001 (0345430239BUY).
Published: As Colonisation: Down to Earth, Hodder & Stoughton 2000 (0340768681); New English Library 2000 (034076869X).
Original in: English.
Translation: Italian by Carlo Boriello as Colonizzazione: Fase 2, Fanucci 2000.

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Turtledove, Harry. Colonization: Aftershocks. Ballantine/Del Rey 2001 (cover art by Viktor Koen).

Turtledove, Harry. Colonization: Aftershocks
Divergence: 1942 CE
Series note: Third and final volume of Colonization, or seventh but not final of Worldwar & Colonization.
Published: Ballantine/Del Rey 2001 (0345430212BUY), 2002 (0345430247BUY).
Original in: English.
Translation: Italian as Colonizzazione: Fase 3, Fanucci 2001.

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Turtledove, Harry. Homeward Bound. Ballantine/Del Rey 2005.

Turtledove, Harry. Homeward Bound
Divergence: 1942 CE
Series note: Epilogue eighth volume to the Worldwar & Colonization series.
Published: Ballantine/Del Rey 2005 (034545846XBUY); Hoddard & Stoughton 2005 (0340734833).