The Gallipoli campaign lasted around 8 months, from the 25th of April, 1915, to the 8th of January, 1916, but the fighting stopped in November sometime. By January everyone had been evacuated.
The battle of Marathon ended very shortly after it began when Persians tried to flee by retreating to ships and swimming in swamps. I believe it was less than 3 hours because it started in midday and...