The police presence in San Diego was heavy, the obvious agenda for the police was to show 'over whelming' force, often boxing Anti-Trump and Pro-Trump demonstrators in together in a protest policing maneuver known as kettling , all though kettling is considered by many to be controversial  it is still widely taught as  a technique to contain protest, more commonly since it was used effectively at the G20 summit in London in April of 2009."The tactics are "to herd the crowd into a pen, known as 'the kettle'… the police will not want groups splintering away from the main crowd." Policing experts say the procedure dictates that officers move protesters to a pre-designated spot. As other protesters join the crowd, the police noose draws gradually tighter. Eventually protesters find themselves surrounded by police specially trained in crowd control. Mounted police can also provide backup. Police may occasionally relieve some of the pressure on the kettle by allowing people to leave – but officers are constantly seeking to maintain control and this is via a designated route. However, anyone determined to stay may be held for hours without access to food and water.