Complex sentence: By 1921 and particularly after the agreement achieved between the Soviet Union and Britain the Soviets decided not to further support the Gilan Republic and as a result the government forces lead by Reza Khan crushed the dispersed forces of the Republic.
Split into simpler sentences: By 1921 and particularly after the agreement reached between the Soviet Union and Britain the Soviets decided to give no further support to the Gilan Republic. As a result, the government forces led by Reza Khan crushed the dispersed forces of the Republic.