Complex sentence: The main French offensive on the Aisne began on 16 April and also achieved considerable tactical success but the attempt to force a strategically decisive battle on the Germans failed and by 25 April the main offensive was suspended.
Split into simpler sentences: The main French offensive on the Aisne began on 16 April and also achieved considerable tactical success. The attempt to force a strategically decisive battle on the Germans was a failure and by 25 April the main offensive was suspended.