They said that they would declare war on Germany
In WW2 the French and Britain said they would declare war on Germany if they attacked Poland. When Nazi Germany invaded Poland France and Britain declared war on Germany. Then Germany stormed French.
Germany wanted an empire like Britain and France had. Unfortunately, Britain and France owned over half of the world between them and Britain also had the world's best navy, so Germany would have to both increase the size of its navy and fight Britain and France for colonial possessions. This damaged relations
Britain and France had offered a guarantee to Poland that if she was attacked by Germany they would come to her aid. When Germany subsequently invaded Poland, Britain and France gave Germany an ultimatum, demanding the withdrawal of German troops from Poland. Failure to do so would result in a state of war.
The more important reason for Britain joining World War 1 was the Schlieffen Plan, that Germany had written up. The plan involved Germany attacking on two fronts; Russia and France. Almost immediately this would of set sparks off within the Triple Entente; Great Britain, Russia and France. The biggest fault of the plan was that Germany would have to go through Belgium to attack France. In 1839, Britain signed a treaty with France stating that they would help Belgium, who were neutral, if they were ever invaded. With Germany wanting to pass through Belgium, Britain were forced to declare war on Germany, something which the Germans had not expected at all. If Britain had left it, essentially Germany would of invaded both France and Belgium, and then would of been able to invade Britain from the South. Germany could of won World War One if Great Britain didn't attack.
Britain and France
France and Great Britain promised Poland that if Germany was ever to invade the poles, they would be on Poland's side of the war that would certainly come.
To help France and Russia defeat Germany. Britain wanted Germany to lose WWI, so they joined France and Russia. Britain was worried that if Germany won WWI, they would be too powerful for England to defeat by themselves, so they joined France and Russia and declared war on Germany.
On 1 September 1939, Germany invaded Poland without a declaration of war. Britain and France had a defence agreement with Poland which stated that they would come to their aid if they were attacked. Britain and France then sent an ultimatum to Germany demanding that their troops withdraw from Poland. Germany ignored the ultimatum so on 3 September 1939, Britain and France declared war on Germany.
Hitler re-armed the Rhineland in an attempt to see how France and Britain would react. The treaties signed by Hitler, especially the Versailles, clearly stated that if the Rhineland was entered and rearmed by Germany they were to be taken out immediately. France and Britain pitied Germany's losses though, and they let Germany have some leeway. In this, Hitler proved that France and Britain were weak and would be too late to stop his larger efforts
That's a strange interpretation of history! In the late 1930's, Britain and France had a defence agreement with Poland which stated that if Poland was attacked by another country, Britain and France would come to its aid. On September 1st 1939, German troops invaded Poland without warning. Britain and France then issued an ultimatum to Germany saying that if they did not immediately withdraw their troops from Poland, 'a state of war would exist'. Germany totally ignored the demand to withdraw, so on September 3rd 1939, Britain and France jointly declared war on Germany.
Well, Russia and Germany wanted to split Poland, so France and Great Britain sent typical troops to fight the battle, this was done in the common style of the time of warfare, only Germany used special tactics which was a "Blitzkrieg". The French typically were a weak ally of Great Britain only because they would lose all of France to Germany so easily.