A violation of Belgium's treaty-obligated neutrality will involve the British on the Continent, regardless of whether the Belgians are victims or co-conspirators in the violation. The only way to avoid the August declaration of war by Britain is for the Germans not to go through Belgium. The most Belgian acquiescence does is make sure the British also declare war on Belgium for violating the Treaty of London (1839).
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Without the sinking of the Lusitania in 1915, you still haven't changed the basic naval facts that make the U.S. a supplier to the Entente instead of the Central Powers, or Woodrow Wilson's basic pro-British slant. So you still get a Zimmerman Telegram in 1917 by a Germany frustrated by the U.S., which is broken by British cryptographers and provokes U.S. entry into the war.
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Without the sinking of the Lusitania in 1915, you still haven't changed the basic naval facts that make the U.S. a supplier to the Entente instead of the Central Powers, or Woodrow Wilson's basic pro-British slant. So you still get a Zimmerman Telegram in 1917 by a Germany frustrated by the U.S., which is broken by British cryptographers and provokes U.S. entry into the war.