The world's military spending is at an all-time high.The Stockholm International Peace Research Institutereports that total spending was $1.8 trillion in 2018.SIPRI Senior Researcher Pieter Wezeman calls it a "worrying trend."Total spending last year was 76 percent higher than it was in 1998,the lowest year since the end of the Cold War.Military spending began rising after the September 11, 2001, terror attacks,which killed almost 3,000 people in the United States.The U.S. accounts for more than a third of world military spending.Experts say the American military remains the world's strongest.It has 11 aircraft carriers, a powerful nuclear weapons supply,new fighter airplanes and about 2.1 million troops.China is now the world's second-largest military spender.It went from just 2 percent of the world's military budget in 1990 to 14 percent in 2018.China built two aircraft carriers in the past 10 years, and a third one is in production.It has developed its own modern fighter planes.And, its troop numbers have grown to more than 2.5 million.China is also investing in new technologies,including weapons that would fly at five times the speed of sound.Wezeman says the speedy progress China has madehas been seen "as a threat by its neighbors."In reaction, India has increased its military spendingby more than $11 billion in just three years.It now comes in fourth in military budgets, behind Saudi Arabia.Last year, Russia dropped out of the top five spending countries.But it still has NATO's attention after invading Georgia in 2008and annexing part of Ukraine in 2014.The 29 NATO countries spent $963 billion-- 53 percent of world military spending -- in 2018.That number is likely to increase as the United States continues to pressure NATO alliesto spend 2 percent of their gross domestic product on defense."We can't let countries off the hook," said U.S. Defense Secretary Mark Esper Saturdayat the Royal United Services Institute in London."You can't simply substitute and say,'Well, my 2 percent is going to go to technology,or I'm going to build infrastructure.' We need real capability."